Pre-emption, congestion control, and tx/rx alignment for nr v2x ue with limited power

ABSTRACT

A method and apparatus are provided for pre-emption, congestion control, and Tx/Rx alignment for use by a partial sensing UE. A method includes measuring resources within a first window; determining a number of the measured resources having an RSSI greater than a first threshold; determining a CBR based on the measured number of resources; and determining a CR limit based on the determined CBR and transmission priority. Determining the CBR based on the measured number of resources includes comparing a total number of measured resources within the first window to a second threshold; in response to the total number of measured resources being less than the second threshold, determining the CBR as a pre-configured CBR; and in response to the total number of measured resources being greater than or equal to the second threshold, determining the CBR based on a ratio of the number of the measured resources having the RSSI greater than the first threshold to the total number of measured resources within the first window.

PRIORITY

This application is a continuation of U.S. Ser. No. 17/410,585, whichwas filed in the United States Patent and Trademark Office (USPTO) onAug. 24, 2021, and is based on and claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Nos. 63/171,376,63/161,639, 63/127,497, 63/090,074, and 63/089,762, which were filed inthe USPTO on Apr. 6, 2021, Mar. 16, 2021, Dec. 18, 2020, Oct. 9, 2020,and Oct. 9, 2020, respectively, the entire content of each of which isincorporated herein by reference.

FIELD

The present disclosure relates generally to new radio (NR)vehicle-to-everything (V2X) enhancement, and more particularly, totechniques for pre-emption, congestion control, and transmission(Tx)/reception (Rx) alignment for use by user equipments (UEs) withlimited power.

BACKGROUND

In NR V2X, Mode 2 resource selection can be used by UEs to selectresources for transmission. Generally, this is two-step procedure inwhich 1) a UE senses the channel to find free (not-reserved) resources,and 2) the UE selects resources based on sensing results.

In Mode 2, a UE establishes a sensing window and a resource selectionwindow. In the sensing window, all UEs that are not transmitting arerequired to monitor all subchannels in order to detect sidelink controlinformation (SCI) transmitted by their neighbors. Once SCI is detected,its reference signal received power (RSRP) is measured and a set ofresources can be considered as occupied in future slots (within theresource selection window) based on the measurement. SCI can indicate upto two future resources (i.e., subchannels and slots) as well as aperiodicity for periodic transmissions.

Subsequently, a sensing UE can identify a set of resources that areoccupied in its resource selection window in order to avoid theseresources. However, despite the advantages of this conventionalprocedure in reducing collisions (i.e., interference), it still requireseach UE to continuously monitor all subchannels in order to identify theoccupied resources, thus consuming large amounts of power.

While such high power consumption may be acceptable for vehicle UEs,which often have an abundant power source, it is not usually feasiblefor pedestrian UEs (PUEs), which have a limited power budget. Forexample, PUEs are expected to sleep for extended durations in order topreserve power and then wake up to perform a transmission, thus havinglimited or no sensing capability. Herein, the terms such as “PUE” and“limited-power UE” may be used interchangeably.

A similar behavior has been observed in long-term evolution (LTE), andconsequently, the resource selection procedure therein was updated toinclude partial sensing and random resource selection in order topreserve power. However, despite the possible advantages of randomresource selection and partial sensing for LTE, these methods offerlimited protection against collisions between neighboring UEs.Consequently, they are not favorable for NR V2X applications, which areexpected to have stricter reliability and latency requirements ascompared to their LTE-based counterparts.

In addition, unlike LTE, NR PUEs are expected to receive messages fromtheir neighboring UEs, and thus, are expected to be listening when otherPUEs are transmitting.

In particular, multiple applications are emerging for NR sidelink (SL)that require power saving. These applications are targeted for use byPUEs as well as for use by UEs for public safety and commercial uses(e.g., in a smart home, a smart factory, etc.). In these applications,it may be important for neighboring UEs to exchange information whileutilizing power saving techniques to preserve their limited power source(e.g., by using partial sensing or random resource selection). However,if the exact partial sensing/random selection procedures of LTE areused, there would be no guarantee that Tx and Rx sensing and resourceselection windows are aligned, thus offering no guarantee on a UE'sability to reach its neighbors. Essentially, the random resourceselection and partial-sensing based resource selection techniques of LTEare not readily applicable to NR V2X because: 1) LTE was designed withonly periodic traffic in mind, and thus the partial sensing techniquedoes not attempt to avoid collisions with aperiodic traffic; 2) LTEassumes that UEs with limited power will be only transmitting and notreceiving, and thus there is no need for Tx and Rx alignment; 3) NR V2Xhas more stringent reliability and latency constraints than those ofLTE; and 4) coexistence between full sensing and power saving UEs waslimited to avoid collisions.

Accordingly, a need exists for techniques that allow a UE to use partialsensing and random resource selection to save limited power, while stillavoiding collisions with neighboring UEs.

SUMMARY

Accordingly, the present disclosure is designed to address at least theproblems and/or disadvantages described above and to provide at leastthe advantages described below.

An aspect of the disclosure is to provide techniques for Tx and Rxalignment to allow information exchange and mass pre-emption.

Another aspect of the disclosure is to provide pre-emption and resourcereselection enhancements.

Another aspect of the disclosure is to provide techniques forwake-up/sleep (WUS) signaling.

Another aspect of the disclosure is to enhance resource exclusion due tohypothetical SCI.

Another aspect of the disclosure is to provide rules for coexistencebetween power saving and full sensing UEs.

Another aspect of the disclosure is to provide updated congestioncontrol metrics of LTE for use in partial sensing.

In accordance with an aspect of the disclosure, a method is provided fora partial sensing UE. The method includes measuring resources within afirst window; determining a number of the measured resources having areceived signal strength indication (RSSI) greater than a firstthreshold; determining a channel busy ratio (CBR) based on the measurednumber of resources; and determining a channel occupancy ratio (CR)limit based on the determined CBR and transmission priority. Determiningthe CBR based on the measured number of resources includes comparing atotal number of measured resources within the first window to a secondthreshold; performing at least one of (a) or (b): (a) in response to thetotal number of measured resources within the first window being lessthan the second threshold, determining the CBR as a pre-configured CBR,and (b) in response to the total number of measured resources within thefirst window being greater than or equal to the second threshold,determining the CBR based on a ratio of the number of the measuredresources having the RSSI greater than the first threshold to the totalnumber of measured resources within the first window.

In accordance with another aspect of the disclosure, a partial sensingUE is provided. The partial sensing UE includes a transceiver; and aprocessor configured to measure resources within a first window;determine a number of the measured resources having an RSSI greater thana first threshold; determine a CBR based on the measured number ofresources; and determine a CR limit based on the determined CBR andtransmission priority. The processor is further configured to determinethe CBR based on the measured number of resources by comparing a totalnumber of measured resources within the first window to a secondthreshold; and performing at least one of (a) or (b): (a) in response tothe total number of measured resources within the first window beingless than the second threshold, determining the CBR as a pre-configuredCBR, and (b) in response to the total number of measured resourceswithin the first window being greater than or equal to the secondthreshold, determining the CBR based on a ratio of the number of themeasured resources having the RSSI greater than the first threshold tothe total number of measured resources within the first window.

In accordance with another aspect of the disclosure, a partial sensingUE is provided. The partial sensing UE includes a processor; and anon-transitory computer readable storage medium storing instructionsthat, when executed, cause the processor to measure resources within afirst window; determine a number of the measured resources having anRSSI greater than a first threshold; determine a CBR based on themeasured number of resources; and determine a CR limit based on thedetermined CBR and transmission priority. The instructions, whenexecuted, further cause the processor to compare a total number ofmeasured resources within the first window to a second threshold; andperform at least one of (a) or (b): (a) in response to the total numberof measured resources within the first window being less than the secondthreshold, determine the CBR as a pre-configured CBR, and (b) inresponse to the total number of measured resources within the firstwindow being greater than or equal to the second threshold, determinethe CBR based on a ratio of the number of the measured resources havingthe RSSI greater than the first threshold to the total number ofmeasured resources within the first window.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a timeline providing an example of partial sensing;

FIG. 2 is flowchart illustrating a Mode 2 resource selection procedure;

FIG. 3 illustrates an example of UEs monitoring different numbers ofmandatory slots depending on respective UE capabilities, according to anembodiment;

FIG. 4 illustrates an example in which a mandatory slot is used toindicate locations of receiving, sensing, and selection windows,according to an embodiment;

FIG. 5 illustrate alignment between sensing and resource selectionwindows of neighboring UEs, according to an embodiment;

FIG. 6 is flowchart illustrating a method using mandatory slotsaccording to an embodiment;

FIG. 7 illustrates a transmission configuration for a pre-empting UE toprovide replacement resources to a pre-empted PUE according to anembodiment;

FIG. 8 is flowchart illustrating a method of pre-emption of a PUEmonitoring only a subset of slots after resource selection according toan embodiment;

FIG. 9 illustrates an example of resource exclusion based onhypothetical SCI, according to an embodiment;

FIG. 10 illustrates an example of dynamic allocation within a resourcepool between full sensing UEs and PUEs based on a channel busy ratio(CBR), according to an embodiment;

FIG. 11 illustrates a full sensing and a partial sensing approachaccording to an embodiment; and

FIG. 12 illustrates an electronic device in a network environment,according to an embodiment.

DETAILED DESCRIPTION

Hereinafter, various embodiments of the disclosure are described indetail with reference to the accompanying drawings. It should be notedthat the same elements will be designated by the same reference numeralsalthough they are shown in different drawings. In the followingdescription, specific details such as detailed configurations andcomponents are merely provided to assist with the overall understandingof the embodiments of the present disclosure. Therefore, it should beapparent to those skilled in the art that various changes andmodifications of the embodiments described herein may be made withoutdeparting from the scope of the present disclosure. In addition,descriptions of well-known functions and constructions are omitted forclarity and conciseness. The terms described below are terms defined inconsideration of the functions in the present disclosure, and may bedifferent according to users, intentions of the users, or customs.Therefore, the definitions of the terms should be determined based onthe contents throughout this specification.

The present disclosure may have various modifications and variousembodiments, among which embodiments are described below in detail withreference to the accompanying drawings. However, it should be understoodthat the present disclosure is not limited to the embodiments, butincludes all modifications, equivalents, and alternatives within thescope of the present disclosure.

Although the terms including an ordinal number such as first, second,etc., may be used for describing various elements, the structuralelements are not restricted by the terms. The terms are only used todistinguish one element from another element. For example, withoutdeparting from the scope of the present disclosure, a first structuralelement may be referred to as a second structural element. Similarly,the second structural element may also be referred to as the firststructural element. As used herein, the term “and/or” includes any andall combinations of one or more associated items.

The terms used herein are merely used to describe various embodiments ofthe present disclosure but are not intended to limit the presentdisclosure. Singular forms are intended to include plural forms unlessthe context clearly indicates otherwise. In the present disclosure, itshould be understood that the terms “include” or “have” indicateexistence of a feature, a number, a step, an operation, a structuralelement, parts, or a combination thereof, and do not exclude theexistence or probability of the addition of one or more other features,numerals, steps, operations, structural elements, parts, or combinationsthereof.

Unless defined differently, all terms used herein have the same meaningsas those understood by a person skilled in the art to which the presentdisclosure belongs. Terms such as those defined in a generally useddictionary are to be interpreted to have the same meanings as thecontextual meanings in the relevant field of art, and are not to beinterpreted to have ideal or excessively formal meanings unless clearlydefined in the present disclosure.

An electronic device according to an embodiment may be one of varioustypes of electronic devices. The electronic devices may include, forexample, a portable communication device (e.g., a smart phone), acomputer, a portable multimedia device, a portable medical device, acamera, a wearable device, or a home appliance. According to anembodiment of the disclosure, an electronic device is not limited tothose described above.

The terms used in the present disclosure are not intended to limit thepresent disclosure but are intended to include various changes,equivalents, or replacements for a corresponding embodiment. With regardto the descriptions of the accompanying drawings, similar referencenumerals may be used to refer to similar or related elements. A singularform of a noun corresponding to an item may include one or more of thethings, unless the relevant context clearly indicates otherwise. As usedherein, each of such phrases as “A or B,” “at least one of A and B,” “atleast one of A or B,” “A, B, or C,” “at least one of A, B, and C,” and“at least one of A, B, or C,” may include all possible combinations ofthe items enumerated together in a corresponding one of the phrases. Asused herein, terms such as “1^(st),” “2nd,” “first,” and “second” may beused to distinguish a corresponding component from another component,but are not intended to limit the components in other aspects (e.g.,importance or order). It is intended that if an element (e.g., a firstelement) is referred to, with or without the term “operatively” or“communicatively”, as “coupled with,” “coupled to,” “connected with,” or“connected to” another element (e.g., a second element), it indicatesthat the element may be coupled with the other element directly (e.g.,wiredly), wirelessly, or via a third element.

As used herein, the term “module” may include a unit implemented inhardware, software, or firmware, and may interchangeably be used withother terms, for example, “logic,” “logic block,” “part,” and“circuitry.” A module may be a single integral component, or a minimumunit or part thereof, adapted to perform one or more functions. Forexample, a module may be implemented in a form of anapplication-specific integrated circuit (ASIC).

In NR V2X, Mode 2 resource selection is a distributed procedure thatallows UEs to select their resources independently from a gNB. Mode 2resource selection is generally a 2-step procedure: 1) a UE senses thechannel to find free (not-reserved) resources; and 2) a UE selectsresources based on sensing results. In this procedure, UEs rely oncontinuous sensing to identify occupied resources by their neighbors andaccordingly select unoccupied resources for their future transmissions.However, continuous sensing has been shown to consume significant power,and thus, is not suitable for PUEs.

FIG. 1 illustrates a timeline providing an example of partial sensing.

Partial sensing was developed for UEs having power consumption limits.It was standardized for LTE and is being standardized for NR. However,these procedures are not currently adopted in NR V2X.

Further, partial sensing was developed for LTE, which is dominated byperiodic traffic, and thus, not readily applicable for NR that canaccommodate aperiodic traffic.

To address the drawbacks above, a work item (WI) discussion wasinitiated for NR V2X Rel-17 to make it more adaptable to power limiteddevices. In particular, the following WI was suggested in RAN meeting#86:

-   -   Resource allocation enhancement:        -   Specify resource allocation to reduce power consumption of            the UEs [RAN1, RAN2]            -   Baseline is to introduce the principle of Rel-14 LTE                sidelink random resource selection and partial sensing                to Rel-16 NR sidelink resource allocation mode 2.            -   Note: Taking Rel-14 as the baseline does not preclude                introducing a new solution to reduce power consumption                for the cases where the baseline cannot work properly.

However, despite the advantages of random resource selection and partialsensing, they offer limited protection against collisions betweenneighboring UEs. Subsequently, if LTE V2X partial sensing and randomresource selection are applied directly, they might not be favorable forNR V2X applications which are expected to require more strictreliability and latency when compared to their LTE-based counterparts.

In addition, unlike LTE, NR power-limited UEs are expected to receivemessages from their neighboring UEs, and thus, they are expected to belistening when others are transmitting.

More specifically, multiple applications are emerging for NR SL thatrequire power saving. In these applications, it is important thatneighboring UEs exchange information while utilizing power savingtechniques to preserve their limited power source (e.g., by usingpartial sensing or random resource selection). Hence, if the exactpartial sensing/random selection procedures of LTE are used there wouldbe no guarantee that Tx and Rx sensing and resource selection windowsare aligned, thus offering no guarantee on the UE's ability to reach itsneighbors.

1. Mode 2 Resource Allocation in NR Rel-16

In resource allocation Mode 2, a higher layer can request a UE todetermine a subset of resources from which the higher layer will selectresources for physical sidelink shared channel (PSSCHYphysical sidelinkcontrol channel (PSCCH) transmission. To trigger this procedure, in slotn, the higher layer provides the following parameters for thisPSSCH/PSCCH transmission:

-   -   the resource pool from which the resources are to be reported;    -   L1 priority, prio_(TX);    -   the remaining packet delay budget;    -   the number of sub-channels to be used for the PSSCH/PSCCH        transmission in a slot, L_(sub)CH: and    -   optionally, the resource reservation interval, P_(rsvp_TX), in        units of ms.

The following higher layer parameters affect this procedure:

-   -   t2min_SelectionWindow: internal parameter T_(2min) is set to the        corresponding value from higher layer parameter        t2min_SelectionWindow for the given value of prio_(TX).    -   SL-ThresRSRP_pi_pj: this higher layer parameter provides an RSRP        threshold for each combination (p_(i), p_(j)), where p_(i) is a        value of the priority field in a received SCI format 0-1 and        p_(j) is a priority of the transmission of the UE selecting        resources; for a given invocation of this procedure,        p_(j)=prio_(TX).    -   RSforSensing selects if the UE uses the PSSCH-RSRP or PSCCH-RSRP        measurement, as defined in subclause 8.4.2.1.    -   reservationPeriodAllowed    -   t0_SensingWindow: internal parameter T₀ is defined as the number        of slots corresponding to t0_SensingWindow ms.

The resource reservation interval, P_(rsvp_TX), if provided, isconverted from units of ms to units of logical slots, resulting inP′_(rsvp_TX), and (t₀ ^(SL), t₁ ^(SL), t₂ ^(SL), . . . ) denotes the setof slots which can belong to a sidelink resource pool.

FIG. 2 is flowchart illustrating a Mode 2 resource selection procedure.

Referring to FIG. 2 :

-   -   Step 1. A candidate single-slot resource for transmission        R_(x,y) is defined as a set of L_(subCH) contiguous sub-channels        with sub-channel x+j in slot t_(y) ^(SL), where j=0, . . . ,        L_(subCH)−1. The UE shall assume that any set of L_(subCH)        contiguous sub-channels included in the corresponding resource        pool within the time interval [n+T₁,n+T₂] correspond to one        candidate single-slot resource, where selection of T₁ is up to        UE implementation under 0≤T₁≤T_(proc,1), where T_(proc,1) is        TBD; If T_(2min) is shorter than the remaining packet delay        budget (in slots) then T₂ is up to UE implementation subject to        T_(2min)≤T₂≤remaining packet budget (in slots), otherwise T₂ is        set to the remaining packet delay budget (in slots). The total        number of candidate single-slot resources is denoted by        M_(total).    -   Step 2. The sensing window is defined by the range of slots        [n−T₀,n−T_(proc,0)), where T₀ is defined above and T_(proc,0) is        TBD. The UE shall monitor slots which can belong to a sidelink        resource pool within the sensing window except for those in        which its own transmissions occur. The UE shall perform the        behavior in the following steps based on the decoded PSCCH and        the measured RSRP in these slots.    -   Step 3. The internal parameter Th(p_(i)) is set to the        corresponding value from higher layer parameter        SL-ThresRSRP_pi_pj for p_(j) equal to the given value of        prio_(TX) and each priority value p_(i).    -   Step 4. The set S_(A) is initialized to the set of all the        candidate single-slot resources.    -   Step 5. The UE shall exclude any candidate single-slot resource        R_(x,y) from the set S_(A)if it meets all the following        conditions:        -   a. The UE has not monitored slot t_(m) ^(SL) in Step 2.        -   b. For any periodicity value allowed by the higher layer            parameter reservationPeriodAllowed and a hypothetical SCI            format 0-1 received in slot t_(m) ^(SL) with “Resource            reservation period” field set to that periodicity value and            indicating all subchannels of the resource pool in this            slot, condition c in Step 6 would be met.    -   Step 6. The UE shall exclude any candidate single-slot resource        R_(x,y) from the set S_(A)if it meets all the following        conditions:        -   a. the UE receives an SCI format 0-1 in slot t_(m) ^(SL),            and “Resource reservation period” field, if present, and            “Priority” field in the received SCI format 0-1 indicate the            values P_(rsvp_RX) and prio_(RX), respectively;        -   b. the RSRP measurement performed, according to received SCI            format 0-1, is higher than Th(prio_(RX));        -   c. the SCI format received in slot t_(m) ^(SL) or the same            SCI format which, if and only if the “Resource reservation            period” field is present in the received SCI format 0-1, is            assumed to be received in slot(s) t_(m+q×P′) _(rsvp_RX)            ^(SL) determines the set of resource blocks and slots which            overlaps with R_(x,y+j×P′) _(rsvp_TX) for q=1, 2, . . . , Q            and j=0, 1, . . . , C_(resel)−1. Here, P′_(rsvp_RX) is            P_(rsvp_RX) converted to units of logical slots,

$Q = \left\lceil \frac{T_{scal}}{P_{{rsvp}\_{RX}}} \right\rceil$

if P_(rsvp_RX)<T_(scal) and n′−m≤P′_(rsvp_RX), where t_(n′) ^(SL)=n ifslot n belongs to the set (t₀ ^(SL), t₁ ^(SL), . . . , t_(T) _(max)^(SL)), otherwise slot t_(n′) ^(SL) is the first slot after slot nbelonging to the set (t₀ ^(SL), t₁ ^(SL), . . . , t_(T) _(max) ^(SL));otherwise Q=1. T_(scal) is TBD.

-   -   Step 7. If the number of candidate single-slot resources        remaining in the set S_(A) is smaller than 0.2·M_(total), then        Th(p_(i)) is increased by 3 dB for each priority value Th(p_(i))        and the procedure continues with Step 4.    -   Step 8. UE shall report remaining of set S_(A) to higher layers,        and high layer then randomly selects a candidate resource for        transmission.

2. Partial-Sensing/Random Based Mode 2 Resource Selection Procedure inLTE V2X

If partial sensing is configured by higher layers then the followingsteps are used:

-   -   1) A candidate single-subframe resource for PSSCH transmission        R_(x,y) is defined as a set of L_(subCH) contiguous sub-channels        with sub-channel x+j in subframe t_(y) ^(SL), where j=0, . . . ,        L_(subCH)−1. The UE shall determine by its implementation a set        of subframes which consists of at least Y subframes within the        time interval [n+T₁, n+T₂], where selections of T₁ and T₂ are up        to UE implementations under T₁≤4 and T_(2min)(prio_(TX))≤T₂≤100,        if T_(2min)(prio_(TX)) is provided by higher layers for        prio_(TX), otherwise 20≤T₂≤100. UE selection of T₂ shall fulfil        the latency requirement and Y shall be greater than or equal to        the high layer parameter minNumCandidateSF. The UE shall assume        that any set of L_(subCH) contiguous sub-channels included in        the corresponding PSSCH resource pool (described in 14.1.5)        within the determined set of subframes correspond to one        candidate single-subframe resource. The total number of the        candidate single-subframe resources is denoted by M_(total).    -   2) If a subframe t_(y) ^(SL) is included in the set of subframes        in Step 1, the UE shall monitor any subframe t_(y-k×P) _(step)        ^(SL), if k-th bit of the high layer parameter        gapCandidateSensing is set to 1. The UE shall perform the        behavior in the following steps based on PSCCH decoded and        S-received signal strength indication (RSSI) measured in these        subframes.    -   3) The parameter Th_(a,b) is set to the value indicated by the        i-th SL-ThresPSSCH-RSRP field in SL-ThresPSSCH-RSRP-List where        i=a*8+b+1.    -   4) The set S_(A) is initialized to the union of all the        candidate single-subframe resources. The set S_(B) is        initialized to an empty set.    -   5) The UE shall exclude any candidate single-subframe resource        R, from the set S_(A) if it meets all the following conditions:        -   1.—the UE receives an SCI format 1 in subframe t_(m) ^(SL),            and “Resource reservation” field and “Priority” field in the            received SCI format 1 indicate the values P_(rsvp_RX) and            prio_(RX), respectively according to Subclause 14.2.1.        -   2. —PSSCH-RSRP measurement according to the received SCI            format 1 is higher than Th_(prio) _(TX) _(,prio) _(RX) .        -   3.—the SCI format received in subframe t_(m) ^(SL) or the            same SCI format 1 which is assumed to be received in            subframe(s) t_(m+q×P) _(step) _(×P) _(rsvp_RX) ^(SL)            determines according to 14.1.1.4C the set of resource blocks            and subframes which overlaps with R_(x,y+j×P′) _(rsvp_RX)            for q=1, 2, . . . , Q and j=0, 1, . . . , C_(reset)−1. Here,

$Q = \frac{1}{P_{{rsvp}\_{RX}}}$

if P_(rsvp_Rx)<1 and y′−m≤P_(step)×P_(rsvp_RX)+step, where t_(y′) ^(SL)is the last subframe of the Y subframes, and Q=1 otherwise.

-   -   6) If the number of candidate single-subframe resources        remaining in the set S_(A) is smaller than 0.2·M_(total), then        Step 4 is repeated with Th_(a,b) increased by 3 dB.    -   7) For a candidate single-subframe resource R_(x,y) remaining in        the setS_(A), the metric E_(x,y) is defined as the linear        average of S-RSSI measured in sub-channels x+k for k=0, . . . ,        L_(subCH)−1 in the monitored subframes in Step 2 that can be        expressed by t_(y-P) _(step) _(*j) ^(SL) for a non-negative        integer j.    -   8) The UE moves the candidate single-subframe resource R_(x,y)        with the smallest metric E_(x,y) from the set S_(A) to S_(B).        This step is repeated until the number of candidate        single-subframe resources in the set S_(B) becomes greater than        or equal to 0.2 M_(total).    -   9) When the UE is configured by upper layers to transmit using        resource pools on multiple carriers, it shall exclude a        candidate single-subframe resource R_(x,y) from S_(B)if the UE        does not support transmission in the candidate single-subframe        resource in the carrier under the assumption that transmissions        take place in other carrier(s) using the already selected        resources due to its limitation in the number of simultaneous        transmission carriers, its limitation in the supported carrier        combinations, or interruption for radio frequency (RF) retuning        time. The UE shall report set S_(B) to higher layers.

When transmission based on random selection is configured by upperlayers and the UE is configured by upper layers to transmit usingresource pools on multiple carriers, the following steps are used:

-   -   1) A candidate single-subframe resource for PSSCH transmission        R_(x,y) is defined as a set of L_(subCH) contiguous sub-channels        with sub-channel x+j in subframe t_(y) ^(SL), where j=0, . . . ,        L_(subCH)−1. The UE shall assume that any set of L_(subCH)        contiguous sub-channels included in the corresponding PSSCH        resource pool (described in 14.1.5) within the time interval        [n+T₁, n+T₂] corresponds to one candidate single-subframe        resource, where selections of T₁ and T₂ are up to UE        implementations under T₁≤4 and TTX₂ _(2min) , if TTX_(2min) is        provided by higher layers for prio_(TX), otherwise 20≤T₂≤100. UE        selection of T₂ shall fulfil the latency requirement. The total        number of the candidate single-subframe resources is denoted by        M_(total).    -   2) The set S_(A) is initialized to the union of all the        candidate single-subframe resources. The set S_(B) is        initialized to an empty set.    -   3) The UE moves the candidate single-subframe resource R_(x,y)        from the set S_(A) to S_(B).    -   4) The UE shall exclude a candidate single-subframe resource        R_(x,y) from S_(B)if the UE does not support transmission in the        candidate single-subframe resource in the carrier under the        assumption that transmissions take place in other carrier(s)        using the already selected resources due to its limitation in        the number of simultaneous transmission carriers, its limitation        in the supported carrier combinations, or interruption for RF        retuning time. The UE shall report set S_(B) to higher layers.

3. Tx and Rx Alignment for Partial Sensing UEs

In the Rel-17 sidelink enhancement WI, unlike its LTE rival, multipleapplications are emerging that require power saving. These applicationsare targeted for PUEs, and also for UEs in public safety and commercialuse cases (e.g., smart homes, smart factories, etc.). In theseapplications, it is important for both transmitters and receivers toutilize power saving techniques to preserve their limited power source(e.g., by using partial sensing or random resource selection). Further,enhancements for sensing pattern alignment are needed to allow forbi-directional communications. In other words, for partial sensing, itis important to align the resource selection window of the Tx UE withthe receiving window of the neighboring Rx UEs in order to allow theexchange of transport blocks (TBs) between the UEs. This alignmentnaturally exists for full sensing UEs, which have a continuous receivingwindow, i.e., all slots are monitored for potential TB reception unlessa UE is transmitting.

In accordance with an embodiment of the disclosure, to achievealignment, the following techniques are provided:

Technique 1:

Unlike in Rel-16 NR V2X, in Rel-17 it is prospected that some UEs (e.g.,PUEs) will not be continuously monitoring all subchannels in order tosave power. These UEs can either monitor some slots, or in some cases,only a subset of subchannels in some of the slots, e.g., similar to thepartial sensing procedure in LTE V2X Rel-14. This partial sensingprocedure is mainly aimed towards reducing the power consumption byallowing a UE to turn off its RF circuitry. Despite its advantages, thisprocedure introduces a new challenge as it requires time alignmentbetween UEs in order to be able to exchange information. To address thisdrawback, a set of slots are defined, during which all UEs are mandatedto be in the receiving mode. That is, mandatory slots are identified inwhich all UEs are required to be monitoring for alignment. By usingthese mandatory slots UEs are able to acquire Tx and Rx alignmentinformation.

Before describing this procedure in more detail, the following threewindows are described:

-   -   a. Receiving window: A UE is active and monitoring the resources        for potential packet transmissions by its neighbors.    -   b. Sensing window: The UE is monitoring the resources for        potential packet transmissions and also identifying the        resources that are reserved by its neighboring UEs in the future        (e.g., the future reservations indicated in the SCIs). The        sensing window can overlap with the receiving window as the        sensing can be considered as a subset of the receiving process.        That is, the sensing involves decoding the SCI information which        is also part of the receiving process.    -   c. Resource selection window: The UE identifies a set of        potential candidate resources that can be used to transmit its        TB. This set is passed to the higher layers for selection. The        candidate resources are selected based on the information        obtained in the sensing window.

In accordance with an embodiment of the disclosure, a method for usingmandatory slots for Tx and Rx alignment can be summarized as follows:

First, a set of slots are identified and are required to be monitored byall UEs (referred to herein as the mandatory slots) either per bandwidthpart (BWP), per resource pool, or a combination thereof. These resourcescan also be pre-configured per resource pool or per BWP. In addition,the mandatory slots can be set as one or more resource pools. In thiscase, UEs will be required to stay awake during these resource pools.Alternatively, the mandatory slots can be set as a specific subset of aresource pool (e.g., the first X slots of a resource pool). In themandatory slots, Tx and Rx alignment information will be sent, and thus,all the UEs are to be active and in the receiving mode in order toacquire this information.

Alternatively, the UEs may be required to monitor only a subset of thesidelink subchannels in the mandatory slots in order to further preservepower.

The mandatory slots can also be periodic to reduce the signalingoverhead. The number and frequency of occurrence of these slots candepend on the CBR and the monitored traffic priorities.

To further reduce the power consumption for monitoring the mandatoryslots, these slots can also be divided into multiple categories, wherebya first category must be monitored by all UEs and following categoriescan be monitored by more capable UEs. A UE's capability can be signaledto neighboring UEs either in the PSCCH/physical sidelink feedbackchannel (PSFCH) or indicated via MAC control element (CE) in the PSSCH.

FIG. 3 illustrates an example of UEs monitoring different numbers ofmandatory slots depending on respective UE capabilities, according to anembodiment.

As illustrated in FIG. 3 , a Type A UE is capable of monitoring 4mandatory slots, while a Type B UE is only capable of monitoring 2mandatory slots over the same time period.

Using the mandatory slots, a 2-step procedure is provided to align theTx and Rx UEs. In particular, in the first step, alignment informationis sent in the mandatory slots and specifies the location and length ofthe receiving, sensing, and resource selection windows. Once thisinformation is obtained, each UE within the area can: 1) select itscandidate resources for potential transmission; 2) identify the sensingwindow over which it should detect the SCIs to figure out the occupiedresources; and 3) identify the receiving window in which it should beactive and receiving data from its neighboring UEs.

In the mandatory slots, either a full sensing UE, a super UE (e.g., aroad side unit (RSU), a gNB, a cluster head, etc.), or a UE providingthe sync source can send information regarding the receiving, sensing,and resource selection windows. Alternatively, it can only provideinformation about the receiving window only, whereby the resourceselection and the sensing windows can be selected as subsets of thereceiving window by each UE individually.

FIG. 4 illustrates an example in which a mandatory slot is used toindicate locations of receiving, sensing, and selection windows,according to an embodiment.

As illustrated in FIG. 4 , the receiving and sensing windows areselected to be identical.

Alternatively, the selection of the resource selection window for eachUE can be up to UE implementation. In other words, each UE can selectits resource selection independently after obtaining the informationabout the other UEs' sensing and receiving windows in the mandatoryslot(s).

A full sensing UE that performs alignment can be proactively activated(e.g., randomly), can be selected by the RSU or gNB, or can only belimited to being either an RSU or a gNB if present in the area.

When more information should be sent for alignment (e.g., to specifymore than one sensing and resource selection window), the number ofmandatory slots can be extended in the current period (when periodic) bysignaling in the first mandatory slot. For example, the super UE canindicate in the first mandatory slots that additional mandatory slotsfor this period will exist. This can be done by using an SCI andreserving future resources or by sending a MAC CE in the PSSCH. Examplesof the information to be sent include one or more receiving, sensing,and resource selection windows. This information can be provided perpriority. The indicated receiving, sensing and resource selectionwindows can be selected to be periodic in order to reduce the overhead.

Alternatively, to reduce the signaling overhead, longer receiving,sensing, and resource selection windows can be signaled (i.e., havingone longer receiving window instead of multiple short windows to reducethe signaling overhead). A longer window can be signaled by SCI or a MACCE in the PSSCH. However, this overhead reduction comes at the expenseof longer latency as the UE will have to wait until a next window to beable to transmit.

Additionally, the signaled sensing windows can be associated withspecific priority levels. For example, one receiving/sensing window canbe given higher priority, and thus, it should be monitored by all UEs,whereas another receiving/sensing window can be associated with a lowerpriority level, and thus, may or may not be monitored by all UEs toreduce the power consumption.

Sizes of the signaled windows can be selected based on the CBR, thenumber of sensed UEs, or the traffic priority in order to reduce thecollision probability. In particular, the larger the number of activeUEs and the higher their traffic priority will result in longer sensingand resource selection windows to allow for more resources forselection. To ensure that all UEs can reach one another, the selectedsensing and resource selection windows may be aligned and overlapped asillustrated in FIG. 5 .

FIG. 5 illustrate alignment between sensing and resource selectionwindows of neighboring UEs, according to an embodiment.

As illustrated in FIG. 5 , the receiving and sensing windows areselected to be identical.

To further utilize the benefits of the mandatory slots, the mandatoryslots may also be used to indicate the following:

-   -   a. In case of random resource selection, the mandatory slots can        be used by the super UE to provide information about a receiving        window to be monitored by all random resource selection UEs in        order to receive the transmitted messages. This receiving window        can be different than that for UEs using partial sensing and can        also be periodic. In addition, all random resource selection UE        transmissions or random transmissions with a given priority can        be restricted to be transmitted during the receiving window        selected for the random resource selection UEs, the receiving        window selected for partial sensing UEs, or a combination        thereof, to ensure that the message can be received. The length        of the receiving window can also be increased as the system        becomes more occupied to reduce the chances of collisions (e.g.,        when the CBR is above a certain threshold).    -   b. The super UE performing the alignment can also forward the        information in case of high priority traffic in the slots that        need to be monitored to ensure that the high priority traffic        can be reached by all of the UEs in the area.    -   c. The super UE can also use a mandatory slot to initiate a mass        pre-emption. In particular, all UEs within the same geographical        area can be pre-empted for a given window. This may be        specifically helpful when high priority packets are to be        transmitted (e.g., emergency vehicle approaching intersection        and want to request other vehicles to stop for it to pass).        Alternatively, mass pre-emption can be used to target only a        subset of the UEs (e.g., one or more categories) or also for        transmission with priority lower than a threshold.    -   d. Mandatory slots can be used to send discontinuous reception        (DRX) information by the super UE, which helps in aligning the        DRX cycles of neighboring UEs within the area, in order to        ensure that the super UE and the neighboring UEs can exchange        information. This may be especially helpful for use in groupcast        and/or broadcast in which it is not straightforward to exchange        the DRX information between neighboring UEs due to the        connectionless mode of operation. This can also help reduce        overhead in aligning unicast transmissions of neighboring UEs.        For example, one DRX alignment message by the super UE can        complete the alignment for many unicast transmissions within one        area.

As described above, according to Technique 1, all UEs may be mandated tomonitor one or more slots per resource pool or per BWP. As such, theseslots can be used to align the transmissions/receptions of all UEswithin a geographical area.

Additionally, a full sensing/super UE may be allowed to transmitalignment information (between sensing and selection windows ofneighboring UEs in case of partial sensing or a sensing window in caseof random selection) in these alignment slots. The UE can also use theseslots to retransmit high priority traffic to ensure that it will reachall UEs within a geographical area.

The full sensing/super UE may also use mandatory slots to providealignment information for UEs performing random resource selection, toensure that they can also be reached and able to exchange information.

Further, the full sensing/super UE may request mass pre-emption to allowfor higher priority transmissions to be successfully transmitted.Further, mass-preemption can also target a subset of UEs or UEtransmissions with priority below a certain threshold.

The full sensing/super UE may also send DRX alignment information in themandatory slots in order to reduce overhead and facilitate an exchangeof TBs between neighboring UEs.

Technique 2:

To reduce complexity of the 2-step procedure for Tx and Rx alignmentdescribed above, all UEs may transmit and receive in the mandatory slots(unlike the previous procedure, which mandated that all UEs, except thesuper UE, will only receive during the mandatory slots). In particular,for each resource pool, a set of mandatory slots can be pre-configured.These slots can be periodic, e.g., with a periodicity that depends onthe CBR and a priority of the transmitted traffic. The number of theseslots can also depend on the UE traffic priority (e.g., the number ofaccessible slots per period in case of periodic can be increased forhigher priorities). This helps reduce collision with higher priorityUEs.

In addition, the number of mandatory slots per period (in case ofperiodic) can also increase with CBR (i.e., the higher the CBR value,the larger the number of mandatory slots) in order to reduce the chancesof collisions.

For non-periodic mandatory slots, the number of configured mandatoryslots per resource pool can still be dynamically chosen based on thepriority and the CBR. In these mandatory slots, all partial sensing UEscan be required to be in the receiving mode unless they aretransmitting. That is, these mandatory slots can be considered as a partof the sensing/receiving window for these UEs.

In some cases, the receiving and sensing windows within the mandatoryslots can be equal to each other. Further, the receiving and sensingwindows can be equal to or a subset of the DRX ON duration (either thefull DRX ON duration or a shared part of the DRX ON duration). Inparticular, if a UE is expected to receive and sense for the completeduration in which it is ON or a predefined duration of its ON time, thenthe DRX ON and the mandatory slots are either totally or partiallyoverlapping (i.e., the DRX and the mandatory slots share the sameobjective and can share the same configuration). In particular, themandatory slots can be equal to the full DRX ON duration or a sharedpart of the DRX ON duration and a mandatory slot configuration can bederived from the DRX configuration. For example, the mandatory slots canbe selected to be either the full DRX ON duration, if all DRX cycles arethe same for all UEs (e.g., UEs within a given region or UEs using thesame resource pool) or the first X slots within the DRX ON duration thatis shared among all UEs (i.e., UEs within a given region or UEs usingthe same resource pool) and during this time all UEs are expected to besensing or sensing/receiving, if not transmitting.

Alternatively, the receiving duration can be a subset of the sensingduration in order to save power, since sensing consumes less power thanreceiving. In some cases, the sensing duration can be equal to the DRXON duration (i.e., the UE is always sensing if it is on).

Subsequently, the DRX and the mandatory slots become essentially thesame and the shared DRX configuration can be used to obtain themandatory slots configuration. For example, if all DRX cycles areidentical for all UEs (i.e., all UEs within a certain region or usingthe same resource pool share the same DRX configuration) then themandatory slots can be obtained from the DRX configuration.Alternatively, the mandatory slots can be equal to the shared part ofthe DRX On duration that is common between all UEs within an area.

In addition, the resource selection and sensing windows can also beselected to be a subset of these mandatory slots in order to ensure thatall neighboring UEs are able to exchange data and reduce their impact tofull-sensing UEs. In other words, this can be considered as confiningthe partial sensing UEs to a subset of the slots in order for thepartial sensing UEs to exchange information and also reduce their impacton full sensing UEs, avoiding potential collisions.

The same or a similar procedure can also be applied to UEs performingrandom resource selection, such that they can be required to bereceiving during the mandatory slots or they can be only confined torandomly select their transmission resources within the mandatory slotsor a combination thereof.

DRX information can also be exchanged between neighboring UEs in themandatory slots (e.g., when the mandatory slots are a subset of the DRXon duration and when the DRX cycles are not aligned among neighboringUEs).

As described above, in accordance with Technique 2, a set of mandatoryslots (e.g., periodic) may be pre-configured for each resource poolduring which the partial sensing UEs are required to be receiving. Theperiodicity of the mandatory slots and the number of mandatory slots perperiod can dynamically change and depend on multiple parameters (e.g.,traffic priority, CBR).

Partial sensing UEs may be required to select their resource selectionwindow within the mandatory slots in order to ensure that their TBs canbe received by neighboring UEs.

Further, UEs performing random resource selection may be required toreceive during the mandatory slots in order to receive TBs ofneighboring UEs.

UEs performing random resource selection may be required to randomlyselect their resources within the mandatory slots so that they can reachthe neighboring UEs.

DRX information may be exchanged between neighboring UEs in themandatory slots in some scenarios (e.g., when mandatory slots are asubset of the DRX on duration).

Further, the mandatory slots can partially or fully overlap the DRX ONduration, and thus, the mandatory slot configuration can be either thesame or a subset of the DRX configuration (e.g., the subset of the DRXduration that is shared among all UEs).

FIG. 6 is flowchart illustrating a method using mandatory slotsaccording to an embodiment.

Referring to FIG. 6 , in step 601, all of the UEs monitor pre-configuredmandatory slots. For example, the mandatory slots can be pre-configuredwith a given periodicity per resource pool as described above.

In step 603, a super UE sends alignment information in the mandatoryslots.

In step 605, each of the UEs determines whether the alignmentinformation is received in the monitored mandatory slots.

When a UE receives the alignment information in the monitored mandatoryslots in step 605, the UE adjusts the sensing and resource selectionwindows based on the alignment information received in mandatory slotsin step 607.

In step 609, each of the UEs determines whether a mass pre-emptionrequest is received in the monitored mandatory slots. As describedabove, the super UE may request mass pre-emption for all the UEs withinthe same geographical area for a given window, or target only a subsetof the UEs.

When a UE receives the mass pre-emption request in the monitoredmandatory slots in step 609, the UE cancels all upcoming resourcereservations in step 611.

In step 615, the UEs continues monitoring the mandatory slots.

4. Pre-Emption Procedure Enhancements for Partial Sensing UEs

In NR V2X Rel-16, pre-emption was introduced to allow higher priorityUEs to acquire resources already reserved by lower priority UEs, whichhelps reduce latency and improves the reliability of higher priority UEsby reducing collisions. However, this procedure relies on the fact thatall of the UEs are full sensing UEs, and thus, able to receivepre-emption requests sent by their neighbors. However, this is not thecase for partial sensing UEs, and thus, the pre-emption procedure shouldbe updated.

In addition, when partial sensing UEs are pre-empted, they may require alonger duration to find suitable resources for their transmission, andthus, can incur large delays.

In accordance with an embodiment of the disclosure, differentenhancements to the pre-emption procedure are described below forpartial sensing UEs.

In some cases, a full sensing UE may pre-empt resources selected by aPUE that is performing partial sensing to preserve power. For example,the full sensing UE can have a higher priority traffic with a tightdelay budget. In this case, the PUE will be required to redo the partialsensing procedure in order to find alternative resources, which consumesa large amount of power and incurs long delays.

In addition, due to the limited sensing capabilities of a PUE, there isa chance that the selected resources can be occupied by other UEs,resulting in collisions.

Accordingly, to address these drawbacks, a pre-empting, full sensing UEmay reserve replacement resources for a PUE at a later point in time.This can be done explicitly through SCI signaling, if the selectedresource is within the signaling window. In this case, the SCI mayinclude a flag (either implicit or explicit) that the future resourcesindicated in the SCI are for replacement to the ones taken from thepre-empted UE(s). This information can be carried in the pre-empting SCIbefore the pre-empted slot or in the SCI sent in the pre-empted slot.

Alternatively, the pre-empting UE can indicate suggested resources forthe power limited UE as a MAC CE, if the selected resources,irrespective of the alternate resources, are within or beyond thesignaling window. The MAC CE can be carried in the payload sent in thepre-empted slot or in a slot that triggers the pre-emption.

As described above, in accordance with an embodiment of the disclosure,in case of pre-emption of a PUE by a full sensing UE, the full sensingUE may provide replacement resources to the PUE. The provided resourcescan be signaled in the SCI along with a flag (either implicit orexplicit) or can be sent in a PSSCH by a MAC CE.

FIG. 7 illustrates a transmission configuration for a pre-empting UE toprovide replacement resources to a pre-empted PUE according to anembodiment.

Referring to FIG. 7 , replacement resources can be indicated in SCI(i.e., in the control channel (PSCCH)) or as a MAC CE (i.e., in the datachannel (PSSCH)). Additionally, a flag indicating that futurereservations are replacement resources can be included in 1^(st) or2^(nd) stage SCI (either explicitly or implicitly).

Despite the advantages of resource pre-emption of NR Rel-16, it may notbe readily implementable for partial sensing because, a low priority PUEmay not be receiving at all slots, and thus, may miss the pre-emptionrequest. To address this drawback, in accordance with an embodiment ofthe disclosure, one or more slots may be specified in which the PUE canexpect to receive the pre-emption request. That is, a PUE may monitoronly a subset of slots after resource selection.

These slots can be either at or before slot m-T₃, where m is thepre-empted slot and T₃ is the minimum time required to process thepre-emption request. These slots can also be pre-configured per resourcepool. The number of slots can depend on the priority of thetransmission. In this case, before each transmission, the UE is expectedto monitor one or more slots for pre-emption. These slots can bedifferent from the mandatory slot described above.

In these specific slots, the PUE monitors the subchannels forpre-emption triggering. This trigger can be carried in a PSCCH (e.g., asa resource reservation indication in SCI), in a PSSCH (e.g., as a MACCE), or in a PSFCH (e.g., in the form of a reserved sequence or aspecified sequence offset). The trigger can also be indicated in theslots which are to be monitored by all UEs for Tx/Rx alignment (e.g.,the RSU can trigger a mass pre-emption for a given duration to allowhigher priority traffic to pass with minimal collisions in emergencycases).

The pre-emption triggering can also come from another UE, other than theone that needs the resources. For example, a UE A may want to pre-emptthe resources of a UE C, but is not able to transmit in the predefinedmonitored slots for pre-emption because they are occupied by anotherhigh priority transmission of a UE B. For example, if the UE C is a UEwith limited power and monitoring for pre-emption only in a subset ofslots which are occupied, the UE A cannot send its pre-emption request.In this case, the UE B can trigger the pre-emption on behalf of the UEA, if it detects the potential collision.

More specifically, the UE B can pre-empt the UE C by sending apre-emption request, either on the PSCCH or the PSSCH. When using thePSCCH, the UE B can reserve the future resources occupied by the UE Cand send a flag (either implicit or explicit) in the SCI to indicatethat this pre-emption is on behalf of another UE.

Alternatively, the UE B can send a MAC CE in the PSSCH that indicatesthe future resources and requests a pre-emption. In this case, the UE Bcan also indicate the priority and source ID of the UE requesting thepre-emption (i.e., the UE A). The UE B can proactively request thepre-emption on behalf of the UE when the priority of the UE A is higherthan that of the UE C or when the priority of the UE A is higher than acertain threshold and is higher than that of the UE C (i.e., provideassistance only for very high priority UEs).

Alternatively, this can be done by a request from the UE A. Inparticular, the UE A can send a flag to indicate an assistance requestwhen it is not able to deliver the pre-emption request to the UE C inthe slots monitored by the UE C for pre-emption.

FIG. 8 is flowchart illustrating a method of pre-emption of a PUEmonitoring only a subset of slots after resource selection according toan embodiment.

Referring to FIG. 8 , in step 801, the PUE performs resource selectionand indicates future reservations. Thereafter, in step 803, the PUEmonitors a subset of the resources until a next transmission based on aresource pool configuration.

In step 805, prior to the next transmission, the PUE determines ifpre-emption is active or if a pre-emption request has been received inthe monitored slots.

When pre-emption is not active and no pre-emption request has beenreceived in the monitored slots in step 805, the PUE performs thetransmission in step 811.

However, when pre-emption is active or a pre-emption request has beenreceived in the monitored slots in step 805, the PUE cancels futurereservations in step 807. Thereafter, in step 809, the PUE determines ifreplacement resources have been received.

When the replacement resources have been received in step 809, the PUEperforms the transmission in step 811 using the replacement resources.

However, when no replacement resources have been received in step 809,the PUE reruns a Mode 2 resource selection procedure in step 813, andmonitor a subset of resources again in step 803.

As described above, in accordance with an embodiment of the disclosure,in case of pre-emption of a PUE, one or more slots may be specified tobe monitored by the PUE for pre-emption triggering. These slots can bepre-configured per resource pool. A neighboring UE may assist in sendinga pre-emption request on behalf of the pre-empting UE, when thepre-empting UE is not able to transmit in the resources monitored by thePUE for pre-emption request. The pre-emption assistance can be doneproactively or in response to a request from the pre-empting UE. Thepre-emption assistance can be sent over the SCI or the PSSCH as a MACCE.

Additionally, despite the advantages of resource pre-emption andresource reselection procedures of NR Rel-16, they may lead a PUE tomonitor an unnecessary slot, thereby resulting in unnecessary powerconsumption. To address this drawback, activation/deactivation ofpre-emption and resource reselection checking may be controlled based ontraffic priority, power level, and CBR. In particular, when thetransmission priority of the PUE is the highest, it may not be necessaryto check for pre-emption or resource reselection, and thus, it is betterto sleep and preserve power. In addition, when the CBR is below acertain threshold, it may become highly unlikely to have a pre-emptionor a resource reselection trigger, and thus, the UE may skip themonitoring in order to preserve power. Additionally, when the powerlevel of the UE is below a certain threshold, it may be necessary topreserve the remaining power of the UE, and thus, it may be possible toskip the monitoring of pre-emption and resource reselection triggers.This activation/deactivation of pre-emption and resource reselectionmonitoring can be performed by the UE itself (e.g., based on its powerlevel) or it can be performed at a resource pool level (e.g., when theCBR is below a certain threshold).

As described above, in accordance with an embodiment of the disclosure,each PUE can activate/deactivate the monitoring of pre-emption andresource reselection triggers based on CBR, power level, and/orpriority. The activation/deactivation of pre-emption and resourcereselection monitoring can also be done at the UE level or for all UEsin a given resource pool.

5. Wake-Up/Sleep Signaling for PUEs

In some cases, it may be beneficial to exchange wake-up/sleep (WUS)signals between UEs in order to ensure packet reception or to preservepower. For example, a first UE can signal to a second UE to continuesensing and avoid going to sleep when new payloads are expected to betransmitted in the near future. Alternatively, a sleep signal can besent to allow an Rx UE to sleep earlier, in order to preserve power,when no new payloads are expected in the near future. A Tx UE can alsoindicate a next sensing window to an Rx UE before it goes to sleep(i.e., provide the duration of the sleep) in order to ensure that theyare time aligned.

The exchange of these WUSs can be either done by a physical (PHY) layeror by a higher layer. In particular, 1^(st) stage or 2^(nd) stage SCIcan carry a field to indicate to an Rx UE to either stay awake or tosleep. For example, a 1-bit field can be added to the 1^(st) or 2^(nd)stage SCI to indicate a wake-up signal when it is set to 1 and a sleepsignal otherwise. If extra bits are available, they can be used toindicate a suggested duration of a wake-up or a suggestedsleep-duration. Alternatively, these extra bits can indicate an index toa table that carries a set of wake-up or sleep durations.

To pre-reserve the SCI bits, the sleep or wake-up durations can be alsoindicated implicitly by setting one or more fields in the 1^(st) stageSCI or 2^(nd) stage SCI to predefined values or the sleep or wake-updurations can be pre-configured per resource pool. When the sleep orwake-up durations are pre-configured per resource pool, the SCI willonly need to carry the wake-up/sleep indication.

Alternatively, the wake-up/sleep signals can also be carried in thePSSCH (e.g., as a MAC CE). In this case a 1-bit field can be added toindicate a wake-up signal when it is set to 1 and sleep signalotherwise. If extra bits are available, they can be used to indicate asuggested duration of the wake-up or sleep-duration or to indicate anindex to a table that carries a set of wake-up or sleep durations.

The WUS indication can be also used by a super UE to preserve power ofone or more categories of UEs. For example, a super UE can send a sleeprequest in a mandatory slot that overrides a previously signaledreceiving and resource selection windows for a given duration in time.This request can also be sent in special cases and for only one or moreUE categories (e.g., sensors placed on the road). In this case, thewake-up/sleep indication may be used to preserve the power of these UEcategories.

The impact of WUS indications on alignment between Tx and Rx UEs shouldalso be considered. This issue may be more pronounced when the Rx UE isexpected to receive data from more than one neighboring UEs. Inparticular, requesting a UE to sleep can reduce/eliminate its receivingwindow, and thus, potentially hinder its ability to receive TBs fromother UEs. In addition, requesting the UE to sleep can also prevent theUE from performing adequate sensing to identify its resource selectionwindow.

If a UE is requested to wake-up for a given duration, this indicatesthat it will be receiving a TB during this wake-up time. Hence, it maybe beneficial to avoid transmitting during this period in order not tolose the expected TB. However, this can also impact its resourceselection window.

To address these possible issues, the following approaches may beimplemented: Impact due to sleep request on:

-   -   Receiving window: In some cases, when an Rx UE is receiving from        a Tx UE, the Rx UE may need to exhaust a timer before going to        sleep in order not to miss any incoming TBs from the        transmitting UE. In this case, the UE can reset the timer        related to the Tx UE when it receives a sleep request. However,        it may not be allowed to go to sleep until it resets all of the        timers associated with all potential Tx UEs. In case of Tx and        Rx alignment by a centralized UE (e.g., using the mandatory slot        as described above), a UE may be required to stay awake until        the end of the receiving/sensing window, even if all timers are        reset.    -   Sensing and resource selection windows: For transmission, a UE        doing partial sensing should perform sensing to identify the        occupancy of candidate resources in its resource selection        window. In this case, a UE may disregard a sleep request, if it        has data to transmit and should perform sensing in order to        identify the candidate resources. Impact due to wake-up request        on:    -   Sensing and resource selection window: A wake up request        indicates that data will be arriving in the near future.        However, if it overlaps with a resource selection window, a UE        may end up losing an incoming TB due to a half-duplex issue. To        address this issue, a UE may delay its transmission (if it is        delay tolerant) until the incoming TB is received. In this case,        the UE may still perform the adequate sensing and identify the        candidate slots for transmission, but only consider the        candidates that occur after it receives the incoming TB.    -   Alternatively, the UE may trigger the sensing and resource        selection procedure only after it receives the incoming TB. This        type of delaying can also be based on a priority of the UE that        sent the wake-up signal.

As described above, in accordance with an embodiment of the disclosure,a wake-up/sleep indication, along with a duration, may be explicitlysignaled in 1^(st) stage or 2^(nd) stage SCI or as a MAC CE in a PSSCHto an Rx UE. In both cases, 1-bit can indicate the wake-up or sleepsignal, whereas remaining bits of the field can indicate thewake-up/sleep duration, either explicitly or as an index to apre-configured table.

The wake-up/sleep indication can be implicitly signaled in the 1^(st)stage or 2^(nd) stage SCI by setting one or more fields to pre-definedvalues. In addition, the wake-up/sleep duration can be pre-configuredper resource pool.

A super UE may send a wake-up/sleep request (e.g., a mass sleep/wake-uprequest) in a mandatory slot(s). This request can override previouslysignaled receiving and resource selection windows and may be applied inspecial cases or for one or more UE categories (e.g., sensors placed onthe road).

A UE can reset a wake-up timer after receiving a sleep request from aneighboring UE. Subsequently, the UE can go to sleep if all wake-uptimers are reset, the UE does not have any data to transmit, and the UEis not required to perform sensing/receiving for Tx and Rx alignment

When a UE receives a wake-up request to indicate incoming TB(s), it candelay its sensing and resource selection window until the TB isreceived. Alternatively, it can perform the sensing, but drop theresource selection candidates within the resource selection windowbefore the TB is received.

A distinguishing factor of NR V2X from LTE V2X is the ability to supporthybrid automatic repeat request (HARQ) feedback. In particular, afterunicast and groupcast transmissions, a UE can enable feedbacktransmission by the transmitted SCI when it is supported by the resourcepool. In this case, an Rx UE will either respond back with an ACK/NACK,in case of unicast and groupcast option 2, and only a NACK, in case ofgroupcast option 1.

In NR Rel-16, the ACK/NACK feedback comes in slot ‘a’ which has PSFCHfeedback and is at least K slots after the PSSCH transmission, where Kis equal to 2 or 3 depending on resource pool configuration.

The PSSCH to PSFCH gap should be considered when deciding thewake-up/sleep duration and also when performing the alignment betweenthe Tx and Rx UEs. In particular, when deciding on the wake-up duration,the UE should make sure that it stays awake long enough after itstransmission to receive the HARQ feedback. That is, there are somescenarios in which the UE should be awake and performing sensing afterits receiving window ends. Alternatively, after performing itstransmission, the UE may elect to sleep, in order to preserve power, andthen wake-up before or at the slot in which it expects to receive theHARQ feedback.

In addition, when performing the Tx and Rx alignment, the PSSCH to PSFCHgap should be taken into consideration. In particular, the sensing orreceiving duration of the Tx UE must be extended to be long enough andaligned with the Rx UE so that it can receive the PSFCH feedback.

As described above, in accordance with an embodiment of the disclosure,the PSSCH to PSFCH gap should be considered when selecting thewake-up/sleep durations and when performing the Tx/Rx alignment.

6. Handling of Unknown Slots Due to Missed Sensing

For partial sensing, there may be scenarios in which a UE ends uptransmitting in some slots within a sensing window. In this case, due toa half-duplex constraint, the UE will not be able to detect SCIstransmitted by neighboring UEs, and thus, may not be able to identifywhether one or more of the slots in a resource selection window areoccupied or not.

For full sensing, in NR V2X Rel-16, a UE assumes the presence of ahypothetical SCI in slots that it has not monitored. Subsequently, theUE excludes resources in the resource selection window by assuming thatall configured periods in a resource pool are received in thehypothetical SCI slot. Despite the advantages of this scheme, it may notbe feasible for use with partial sensing as it may result in so manyresources being excluded.

To address this drawback, in accordance with an embodiment of thedisclosure, a UE excludes resources based on a subset of periodsconfigured in a resource pool. The subset can be designed to includeonly a periodicity (P) of PUE transmissions that triggered resourceselection. Alternatively, the subset can include P and all theconfigured periodicities that divide P, or the subset can include themost commonly used periodicities in a given geographical area. Thesubset can also include only the configured periodicities that aresmaller than a threshold.

As described above, in accordance with an embodiment of the disclosure,in case a slot is not sensed in a sensing window for partial sensing dueto a half-duplex constraint, a UE may exclude resources in a resourcesselection window corresponding to a subset of periodicities configuredin a resource pool.

The periodicities considered for resource exclusion can include one or acombination of a periodicity (P) of a transmission that triggered aresource selection, any configured periodicity in the resource pool thatdivides P, the most commonly used periodicities in a given geographicalarea, or configured periodicities that are smaller than a threshold.

As discussed above, a UE may be required to exclude a large number ofslots and subchannels when it is not able to sense a slot in its sensingwindow (e.g., due to the half-duplex constraint). However, an exclusionof such resources may not be necessary for subchannels over which itactually performs transmission.

FIG. 9 illustrates an example of resource exclusion based onhypothetical SCI, according to an embodiment.

Referring to FIG. 9 , a resource pool is configured with 3 subchannelsand a UE A performs a transmission on subchannel 1 in slot m that fallswithin its sensing window. Since the UE A has reserved subchannel 1 inthis slot and actually did transmit in this slot, then it can be assumedthat no other UE was able to send another SCI and/or make a futurereservation during slot m in subchannel 1. Therefore, it may besufficient to assume the presence of the hypothetical SCIs on only thesubchannels that the UE A did not use for its own transmission.Subsequently, the resources to be excluded can be reduced.

If a UE occupies all subchannels within a given slot n, it may not needto exclude any of the resources in its resource selection window. Thistechnique may be applied for partial sensing and full sensing UEs.

As described above, in accordance with an embodiment of the disclosure,a UE may not monitor a slot within its sensing window due to being inthe Tx mode. In these cases, hypothetical SCIs (and the exclusion oftheir corresponding resources in the resource selection window) can beassumed in the subchannels that were not occupied by the UEtransmission.

Accordingly, less resources may be excluded by excluding only a subsetof subchannels within slots in which a UE did not transmit, or excludingonly a subset of the configured periodicities for the resource pool.

7. Coexistence of Transmissions Based on Full Sensing with TransmissionsBased on Power Saving RA Scheme(s) in a Same Resource Pool

To ensure better utilization of a system's resources and avoid resourcesegmentation, it is expected that NR V2X Rel-17 will allow coexistencebetween power saving UEs and regular UEs in the same resource pool.However, sharing a resource pool between PUEs and full sensing UEs canimpede the system performance.

In particular, a power saving UE using random resource selection orpartial sensing can have access to the same resources utilized by fullsensing UEs. Despite the advantages of this scheme, it may create aburden on the full sensing UEs by triggering many resource reselectionsor pre-emptions. In addition, it can also result in many collisionssince UEs that use random resource selection may not monitor theresources before accessing them.

Further, separating the resource pool can lead to inefficientutilization of resources when one is dominating the other.

In accordance with an embodiment of the disclosure, to mitigate thesedrawbacks, a method is provided to dynamically allow/block access ofpower saving UEs in a resource pool. This type of restriction may bebased on a priority of a UE transmission. In particular, UEs performingrandom resource selection or partial sensing and having a priority abovea certain threshold may coexist with full sensing UEs.

This type of restriction may also be based on a measured CBR. Forexample, coexistence may occur when the measured CBR (in case of partialsensing and full sensing UEs) or the given/pre-configured CBR (in caseof UEs performing random resource selection) is above or below a certainthreshold.

In addition, a full sensing UEs may be allowed to coexist in resourcepools configured with random resource selection or partial sensing, ifthe CBR is above a certain threshold in other resource pools (i.e., aCBR measurement can be done over one resource pool only) or when itspriority is above/below a certain threshold.

FIG. 10 illustrates an example of dynamic allocation within a resourcepool between full sensing UEs and PUEs based on CBR, according to anembodiment.

Referring to FIG. 10 , resource pools 1 and 2 are accessible by fullsensing UEs. However, resource pool 1 is accessible by PUEs when CBR isbelow a 1^(st) threshold, and resource pool 2 is accessible by PUEs whenCBR is below a 2^(nd) threshold.

Another approach to limit the negative impact of coexistence is to limitthe power of an initial transmission or subsequent retransmissions ofpower saving UEs when using a shared resource pool. This approach may bebeneficial because the power saving UEs may not perform adequatesensing, and thus, may interfere with higher priority UEs using the sameresource pool. The restriction on the transmit power may be based on atransmission priority.

Additionally, PUEs may be allowed to increase their priority indicationin SCI in order to reduce chances of pre-emption.

For example, a pre-configured increase may be defined for each prioritylevel to prevent pre-emption of power saving UEs when coexisting withfull sensing ones. Some priority levels may be increased by a valuebigger than other priority levels. In addition, the pre-configuredincrease may also depend on resource allocation techniques (e.g., arandom resource selection can have a higher priority increase than apartial sensing).

As described above, in accordance with an embodiment of the disclosure,the coexistence of power saving UEs with full sensing UE may dynamicallyallowed/blocked in one or more resource pools. The restriction forcoexistence between full sensing and power saving UEs in one or moreresource pool can be based on the measured/obtained/pre-configured CBRbeing above or below a certain threshold and/or a priority of a UEtransmission being above a certain threshold.

A CBR may be measured only over one or more resource pools, rather thanall configured resource pools, and the accessible resource pools may bedetermined accordingly.

The transmit power of an initial transmission or subsequenttransmissions of power saving UEs may be limited, when using a sharedresource pool with full sensing UEs. This restriction can depend on thetransmission priority of the power saving UEs.

The power saving UEs may increase priority levels of their transmissionsin order to prevent pre-emption by full sensing UEs. This increase canbe done separately for each priority level and can depend on theresource allocation technique (e.g., random resource allocation can betreated separately than partial sensing UEs).

8. Congestion Control Support for Power Saving Based RA

In LTE and NR V2X, congestion control mechanisms may be used to reducecollisions between neighboring UEs when utilizing a Mode 2 resourceselection procedure. In particular, two congestion control metrics(i.e., CBR and channel occupancy ratio (CR)) are defined, whereby theCBR measures the number of resources within a given window with an RSSIabove a certain threshold. Based on the measured CBR, the UE obtains aCR_(Limit), which governs how many resources a UE can occupy within agiven window. The CR_(Limit) will depend on priority.

In particular, the UE measures a CR that includes the resources it hasconsumed and resources to be consumed with a given window and comparesit against its CR_(Limit). If the measured CR is below the CR_(Limit),then the UE can proceed with its transmission. Despite the advantages ofthese mechanisms, they are not readily applicable for when no or limitedsensing is considered (e.g., random resource selection or partialsensing). To address this issue, in LTE V2X, when partial sensing orrandom resource selection is used and the sensing information is notavailable, the UE uses a pre-configured CBR value in order to obtain itsCR_(Limit). However, despite the simplicity of this technique, it maynot be readily applicable for NR V2X due to its tight reliability andlatency constraints.

In accordance with an embodiment of the disclosure, to address thisconcern, a value of CBR for partial sensing UEs may be redefined andbased on a sensed duration with a given validity. In particular, if a UEonly measured 100 slots out of the previous 1000 slots, then its CBRvalue should be adjusted to consider only the 100 measured slots.

In addition, the validity of the measured CBR should be constrained witha timer. Once the timer has expired, the UE can fall back to apreconfigured value of CBR, if no new measurements are available.

In addition, to ensure the quality of the measured CBR, it can beconsidered as valid only if a certain number of slots are monitoredwithin the CBR measurement window.

Multiple CBR values may be pre-configured per resource pool.Subsequently, the UE can dynamically select one of these pre-configuredCBR values when measurements are not available (e.g., based on itspriority or its last measured CBR if it is not too old).

As described above, in accordance with an embodiment of the disclosure,a value of a CBR may be redefined to consider only resources that fallin the measured slots within the CBR measurement window, in case ofpartial sensing.

Additionally, a CBR validity timer may be defined, whereby the UEutilizes a pre-configured CBR value once the timer expires, if noupdated CBR is obtained through measurements.

Further, a measured CBR may be considered valid if the number ofmeasured slots within the CBR measurement window is above a certainthreshold.

Multiple CBR values may be preconfigured per resource pool and a UE maydynamically select one of these values, e.g., based on the UE'spriority, its previous CBR measurements, or the number of monitoredslots and their occupancy, if these slots are below a threshold, toprovide a valid CBR.

9. Impact of Partial/No Sensing on Resource Re-Selection and Pre-EmptionTriggering

In NR V2X Rel-16, resource re-selection and pre-emption mechanisms wereintroduced to reduce collisions between neighboring UEs. In particular,after a UE selects a resource and before signaling it to neighboring UEsin an SCI, the UE continuously performs sensing. During this period, ifthe UE identifies that a resource was reserved by a neighboring UE, thenit triggers a resource re-selection in order to find a differentresource and avoid the possible collision.

Similarly, after a UE indicates that it reserved a future resource andbefore the actual transmission, the UE continuously performs sensing.During this period, if the UE detects that a neighboring UE with a givenpriority above a threshold reserved the same resource, it triggersresource re-selection and considers the conflicting resource aspre-empted.

An advantage of these mechanisms is that the number of potentialcollisions between neighboring UEs can be reduced as compared to LTEV2X. However, for these mechanisms to work properly, the UE performssensing in order to identify the conflicting resources. However, theimplementation of these schemes may not be straight forward, especiallyin scenarios in which the UE performs partial/opportunistic sensing forresource selection or when a UE that is capable of continuously sensingthe subchannels performs random resource selection (e.g., to meet astrict packet delay budget, save power, or reduce the complexity ofresource selection).

In order to address these issues in accordance with an embodiment of thedisclosure, the following 3 sensing categories will be described, basedon when the UE performs random resource selection and how sensing isdone.

I. A UE continuously/partially/opportunistically senses after randomresource selection only for this transmission opportunity

Before going into the details of this category, the following ishighlighted:

-   -   When a trigger occurs at slot n, a UE randomly selects a        resource for transmission and then performs sensing for resource        re-selection/pre-emption. In this case, the sensing information        is available only after random resource selection. Herein, this        sensing information is referred to as the one belonging to the        current sensing interval and occurs after resource selection.    -   When another trigger occurs at slot m>n, a UE randomly selects a        resource for transmission. Subsequently, the UE performs sensing        for resource re-selection/pre-emption. However, since slot m        occurs after n, some sensing information may be available due to        sensing after slot n, despite that this sensing is not triggered        by the incoming trigger at slot m. This information can be used        to enhance the random resource selection process or for resource        re-selection/pre-emption. Herein, this additional sensing        information is referred to as sensing information belonging to        previous transmission intervals.

In this category, a current approach is that a UE randomly selectsresources for transmission based on its incoming packet (e.g., packetsize and priority) without considering previous sensing results (i.e.,sensing information not belonging to previous transmission intervals).Subsequently, the UE relies only on resource re-selection andpre-emption for collision avoidance. However, a UE may only be able topartially detect aperiodic/periodic future resource reservations by itsneighbors, and thus, there is still a potential for collisions. This canhappen due to 1) the future periodic/aperiodic traffic of one of itsneighbors was indicated at a slot n before the random resource selectiontrigger, or 2) a UE may miss future resource indication due to partialor opportunistic sensing.

Alternatively, a UE may utilize sensing information from previoussensing intervals for resource re-selection and pre-emption. However, amore effective way in utilizing this information is updating theresource selection set in order to avoid selecting a conflictingresource rather than reselecting/pre-empting afterwards.

To address these drawbacks, in accordance with an embodiment of thedisclosure, the following approaches are provided:

Random selection indication: Include a random resource selectionindication, either implicitly or explicitly, in the SCI (i.e., in either1^(st) stage or 2^(nd) stage SCI). For an explicit indication, anadditional field (e.g., 1-bit) can be added to either the 1^(st) or2^(nd) stage SCI to indicate that these resources were randomlyselected, thus suggesting to other UEs to avoid these resources even ifthey have higher priority.

Alternatively, the indication can be done implicitly by setting one ormore SCI fields to specific values. This indication is not limited tothe power-limited UEs and can be used by full sensing UEs that elect toperform random resource selection.

Periodic traffic sensing gap: Restrict a UE to randomly select aresource that is at least X slots after a slot at which a randomresource selection occurs. The objective of this gap is to allow the UEto perform sensing before transmission, thus allowing the UE to performresource reselection and pre-emption to avoid potential collisions. Forexample, this gap can be based on the longest configured period perresource pool to avoid all collisions.

Alternatively, the gap can be set to be equal to a specific threshold inorder to avoid collisions with all periods smaller than the selectedthreshold.

The gap can also be configured based on traffic priority or the mostcommonly used period in the resource pool by traffic type. The thresholdcan also depend on the measured/configured CBR value.

Aperiodic traffic sensing gap: Restrict a UE to randomly select aresource that is at least Y slots after a slot at which a randomresource selection has occurred. The objective of this gap is to allowthe UE to sense aperiodic traffic reservations in order to avoidpotential collisions with aperiodic traffic by resource re-selection orpre-emption. For example, the gap can be set to Y=32 slots, if theresource selection window is equal to 32 in order to avoid 100%collisions or can be set to Y=16 slots in order to avoid 50% collisions.

The selection of the gap can also be based on the traffic priority andlevel of congestion (e.g., it can be higher when the system is congestedwith higher measured/configured CBR value or lower when the traffic hashigher priority).

Sensing intensity adjustment: For partial/opportunistic sensing, a UEmay be required to increase its sensing intensity (i.e., the number ofsensed slots in a given duration) in order to detect potentialcollisions. This change can be based on traffic priority and a level ofcongestion (i.e., measured or pre-configured CBR).

Usage of sensing information from previous transmission intervals whenperforming random resource selection: Before random resource selection,a UE may be required to adjust its random resource selection set toaccount for previous sensing information from previous intervals, ifavailable. This information may be based on sensing done for previoustransmission triggers.

II. UE continuously/partially/opportunistically senses before randomresource selection

Unlike the previous category, UEs can perform sensing before resourceselection. In particular, sensing can occur between a triggering eventand before a random resource selection. Herein, this sensing is referredto as the sensing belonging to this interval. This sensing does notpreclude the UE from using sensing from previous intervals for randomresource selection set adjustment and re-selection/pre-emptiontriggering.

For example, the UE randomly selects resources for transmission based onits incoming packet. These selected resources are obtained from a set ofavailable resources. This set can be adjusted based on the sensinginformation obtained before random selection (either in this sensinginterval or in previous intervals). However, in both cases, collisionscan occur (e.g., if some slots are not monitored in case ofpartial/opportunistic sensing and thus the neighboring UEs reservationscan't be avoided). Additionally, even if sensing is applied, possiblecollisions can also result in collisions as future resource reservationsthat were signaled before the triggering event are not considered.

To address these drawbacks, in accordance with an embodiment of thedisclosure, the following approaches are provided.

Random resource selection set adjustment: Adjust a random resourceselection set to avoid potential collisions with neighboring UEs. Thiscan also be done based on priority.

For example, only resources occupied with high priority UEs can beexcluded from the set of resources for random resource selection. Thisadjustment will be based either on the sensing information belonging tothis interval or the sensing information belonging to previous intervalsif they are close enough in time.

Resource-reselection/pre-emption triggering after resource selection. Inthis case, after random resource selection, a UE may be required totrigger resource re-selection/pre-emption to avoid potential collisions.This reselection/pre-emption can be based on sensing obtained before theresource selection trigger (i.e., belonging to previous intervals) orafter trigger and before random resource selection (i.e., the sensinginformation belonging to this interval). The triggering ofreselection/pre-emption can also be based on priority.

III. UE continuously/partially/opportunistically senses before and afterresource selection for this transmission opportunity

In this case, a UE performs sensing for the current transmissioninterval as follows:

-   -   After triggering event and before random resource selection; and    -   After random resource selection for pre-emption and resource        re-selection.

Despite this sensing, a UE may still fail to detect resourcereservations of neighboring UEs, thus resulting in collisions.

To address this drawback, in accordance with an embodiment of thedisclosure, the following approaches are provided:

Sensing intensity adjustment: For partial/opportunistic sensing, a UEmay be required to increase its sensing intensity (i.e., the number ofsensed slots in a given duration) for a specific duration before orafter the random resource selection. The objective of this switch is totry to detect as many potential collisions as possible. This switch mayalso be dependent on a gap between a resource selection trigger and arandomly selected resource.

This switch may also depend on a priority and level of congestion (i.e.,measured or pre-configured CBR). Even if a UE switches to full sensing,it may not be possible to avoid all collisions since the neighboring UEsindicated reservation can be done before the resource selection trigger.To avoid all collisions, the UE is required to randomly select aresource that is sufficiently far in time to allow for enough sensingafter resource selection.

As described above, in accordance with an embodiment of the disclosure,a UE may flag random resource selections, either implicitly orexplicitly, in 1^(st) or 2^(nd) stage SCI. Subsequently, neighboring UEscan avoid such resource reservations to avoid potential conflicts evenif they have higher priority.

When performing random resource selection, the UE may be required to useresources that are at least X slots away from a slot in which itperforms random resource selection in order to allow for periodictraffic sensing. This X slot gap can be based on configuredperiodicities or the traffic priority or the congestion level (e.g.,measured/configured CBR).

Alternatively, the UE may be required to use resources that are at leastY slots away from a slot in which it performs random resource selectionin order to allow for aperiodic traffic sensing. This Y slot gap can bebased on traffic priority or the congestion level (e.g.,measured/configured CBR).

The UE may temporarily adjust its sensing intensity (i.e., number ofsensed slots in a given duration) to be able to detect potentialcollisions. This adjustment can be done after random resource selectionand be based on gap duration, priority, and/or congestion level.

A UE may use the sensing information from previous transmissionintervals to adjust its random resource selection set, in order to avoidpotential collisions. This can also depend on the priority of thetraffic.

Resource re-selection/pre-emption triggering may occur after randomresource selection based on sensing information obtained in previoustransmission intervals.

10. Techniques for CBR Calculation and Selection of Y Candidate Slotsfor Partial Sensing

Unlike in Rel-16 NR V2X, some UEs (e.g., PUEs), in order to save power,may not be continuously monitoring all slots. These UEs may select asub-set of Y slots in a selection window. A minimum allowed value of Yis (pre)configured and given by parameter minNumCandidateSF. If a slott_(y) ^(SL) is included in the sub-set of Y slots, the UE shall monitorany slot subframe t_(y-k×P) _(step) ^(SL), if the k-th bit of the highlayer parameter gapCandidaleSenrsing is set to 1, where P_(step) is thestep size and is set to 100 in LTE Rel 14 FDD mode and different valuesfor TDD. The standard does not specify how to select Y slots and how toset the is in the bit-map parameter gapCandidateSensing. Accordingly, itmay be up to the PUE to randomly select the Y slots and this may besuboptimal if the system is congested (higher chance of collision).

To address this issue, in accordance with an embodiment of thedisclosure, a system may perform full sensing followed by a number ofpartial sensings, e.g., as illustrated in FIG. 7 .

FIG. 11 illustrates a full sensing and a partial sensing approachaccording to an embodiment.

Referring to FIG. 11 , during the full sensing session, the UE monitorsall slots for a given duration and obtains the system CBR and busy ratiofor each slot (i.e., the number of occupied subchannels in a slot overthe number of subchannels in a slot, herein after referred to as“slot-level CBR”) in the selection window. This information is storedand used in the subsequent partial sensing sessions. More specifically,in each partial sensing session,

a. The system CBR is used to adjust the number of Is in the bit-mapparameter gapCandidateSensinrg. For example, a UE can increase thenumber of monitored sensing occasions (a sensing occasion is a set of Ymonitored slots corresponding to a set bit in the bit map of K) if CBRis relatively high, and vice versa.

b. A UE can sort the slots in the selection window by slot-level CBR,and pick the Y slots with minimum slot-level CBR values. By selectingthe least busy slots, the probability of collision with another UE isreduced.

The slot-level CBR may change in each partial sensing session since theavailable resources in each slot may change after each sensing andselection. Therefore, the Y slots may be different in each partialsensing session.

The number of partial sensing sessions after one full sensing can beadjusted according to the power requirement and entails a tradeoffbetween system tracking accuracy and the amount of power saving.

In an extreme case in which CBR information is somehow given by a higherlayer, the full sensing procedure can be skipped to further save powerfor the PUE. The full sensing procedure can also be skipped if the CBRdetected in previous full sensing session is below a certain threshold.

As described above, in accordance with an embodiment of the disclosure,a full sensing session may be followed by a number of partial sensingsessions. The CBR information from full sensing session is stored andused in the subsequent partial sensing sessions

The number of sensing occasions in each partial sensing can be adjustedaccording to the system CBR. The slots in the selection window can besorted by the slot-level CBR and a UE selects Y slots with the minimumvalues in the partial sensing selection window.

The number of partial sensing sessions following each full sensingsession can be adjusted according to power requirements. When CBRinformation is readily given by a higher layer, the full sensing can beskipped. The full sensing can also be skipped if the CBR measured in aprevious full sensing period is below a threshold.

Inter-UE coordination may be utilized to improve reliability and latencyof a resource selection procedure. In particular, a UE-B may requestassistance for resource allocation from a UE-A, and in response, theUE-A may send a set of resources recommended (e.g., a white-list) or notrecommended (e.g., black-list) to the UE-B. How to use this ‘set ofresources’ for the UE-B is still under discussion.

If the UE-B is undergoing partial sensing, it may select the sub-set ofY slots in the selection window based on the assistance feedback fromthe UE-A. More specifically, the UE-B may sort the slots by the numberof white-listed or black-listed subchannels in each slot, and thenselect Y slots with maximum white-listed subchannels or minimumblack-listed subchannels. These Y candidate slots should be advantageousover randomly selected slots since it contains the information fromtarget UE assistance.

Alternatively, another approach may be implemented to include/excludecertain slot(s) based on the UE assistance feedback. A slot may beincluded in the Y sub-set selection, if the number of white-listedsubchannels in this slot is above a threshold, or a slot may be excludedfrom the Y sub-set, if the number of black-listed subchannels in thisslot is above a threshold.

As described above, in accordance with an embodiment of the disclosure,when a partial sensing UE is requesting UE assistance, the UE may selectY slots with the most white-listed subchannels or with the leastblack-listed subchannels as the candidate slots in the selection window.

A partial sensing UE may include/exclude a slot in the Y sub-set ofselected slots, if the number of white-listed/black-listed subchannelsin the slot is above a threshold.

A scenario that may cost extra power is that a partial sensing UE wakesup frequently to monitor slots in a sensing window. This issue becomesmore pronounced when the UE has a sub-set of distributed slots in aselected window.

In accordance with an embodiment of the disclosure, a simple solution isto limit the sub-set to contain contiguous slots only. This may alsosave messaging overhead, if this UE is providing resource selectionassistance to other UE.

11. Wake-Up Duration Extension for Retransmission and Cross-SlotScheduling

In partial sensing, a UE monitors only slots corresponding to a sub-setof candidate slots in a selection window, and remains asleep/idle forthe rest of the slots. However, this may cause an issue if an Rx UE issending a NACK message to request a re-transmission from another UE,since the re-transmission may be transmitted in a slot that the UE isnot monitoring.

In accordance with an embodiment of the disclosure, to obviate thisissue, an Rx UE may remain awake until it receives a re-transmission andsuccessfully decodes the packet. When the Rx UE knows the slot of there-transmission, it only needs to wake up and monitor that slot.

Alternatively, the Rx UE can give assistance to a Tx UE by sending aresource suggestion in slots that the Rx UE is monitoring.

As described above, in accordance with an embodiment of the disclosure,a partial sensing UE requesting a re-transmission may remain wake untilit receives a retransmission and successfully detects a packet or untila maximum wake time is reached. The partial sensing UE may wake up andmonitor a specific slot for re-transmission, if this slot is known tothe UE.

Additionally, an Rx UE may give assistance to a Tx UE by sending aresource suggestion in slots that the Rx UE is monitoring.

Cross-slot scheduling has also been used in NR Uu for power savingpurposes.

When a UE receives symbols carrying a PDCCH, it does not need to receivethe symbols for a PDSCH of the same slot, since the scheduled PDSCHshould be in a later slot. Accordingly, some proposals have adopted thesame idea to NR SL by indicating a time slot offset between 2^(nd) SCIand data from that of 1^(st) SCI. However, if a PUE undertaking partialsensing is a target UE for a transmission and it successfully decodesthe 1^(st) SCI message in one slot, it may not monitor the correspondingslot of the 2^(nd) SCI and data, and therefore, it fails to receive anddecode the packet.

To solve this problem, in accordance with an embodiment of thedisclosure, a partial sensing UE may wake up and monitor a slot for atransmission of 2^(nd) SCI and data, even though this slot is not one ofthe monitoring slots in a sensing window. That is, if cross-slot isenabled for SL and a partial sensing PUE detects a 1^(st) SCI in a slot,the PUE may wake up and monitor the slot for the corresponding slot of2^(nd) SCI and data, even though this slot is not one of the monitoringslots in the sensing window.

FIG. 12 illustrates an electronic device in a network environment,according to an embodiment.

Referring to FIG. 12 , the electronic device 1201, e.g., a mobileterminal including GPS functionality, in the network environment 1200may communicate with an electronic device 1202 via a first network 1298(e.g., a short-range wireless communication network), or an electronicdevice 1204 or a server 1208 via a second network 1299 (e.g., along-range wireless communication network). The electronic device 1201may communicate with the electronic device 1204 via the server 1208. Theelectronic device 1201 may include a processor 1220, a memory 1230, aninput device 1250, a sound output device 1255, a display device 1260, anaudio module 1270, a sensor module 1276, an interface 1277, a hapticmodule 1279, a camera module 1280, a power management module 1288, abattery 1289, a communication module 1290, a subscriber identificationmodule (SIM) 1296, or an antenna module 1297 including a GNSS antenna.In one embodiment, at least one (e.g., the display device 1260 or thecamera module 1280) of the components may be omitted from the electronicdevice 1201, or one or more other components may be added to theelectronic device 1201. In one embodiment, some of the components may beimplemented as a single integrated circuit (IC). For example, the sensormodule 1276 (e.g., a fingerprint sensor, an iris sensor, or anilluminance sensor) may be embedded in the display device 1260 (e.g., adisplay).

The processor 1220 may execute, for example, software (e.g., a program1240) to control at least one other component (e.g., a hardware or asoftware component) of the electronic device 1201 coupled with theprocessor 1220, and may perform various data processing or computations.As at least part of the data processing or computations, the processor1220 may load a command or data received from another component (e.g.,the sensor module 1276 or the communication module 1290) in volatilememory 1232, process the command or the data stored in the volatilememory 1232, and store resulting data in non-volatile memory 1234. Theprocessor 1220 may include a main processor 1221 (e.g., a centralprocessing unit (CPU) or an application processor, and an auxiliaryprocessor 1223 (e.g., a graphics processing unit (GPU), an image signalprocessor (ISP), a sensor hub processor, or a communication processor(CP)) that is operable independently from, or in conjunction with, themain processor 1221. Additionally or alternatively, the auxiliaryprocessor 1223 may be adapted to consume less power than the mainprocessor 1221, or execute a particular function. The auxiliaryprocessor 1223 may be implemented as being separate from, or a part of,the main processor 1221.

The auxiliary processor 1223 may control at least some of the functionsor states related to at least one component (e.g., the display device1260, the sensor module 1276, or the communication module 1290) amongthe components of the electronic device 1201, instead of the mainprocessor 1221 while the main processor 1221 is in an inactive (e.g.,sleep) state, or together with the main processor 1221 while the mainprocessor 1221 is in an active state (e.g., executing an application).According to one embodiment, the auxiliary processor 1223 (e.g., animage signal processor or a communication processor) may be implementedas part of another component (e.g., the camera module 1280 or thecommunication module 1290) functionally related to the auxiliaryprocessor 1223.

The memory 1230 may store various data used by at least one component(e.g., the processor 1220 or the sensor module 1276) of the electronicdevice 1201. The various data may include, for example, software (e.g.,the program 1240) and input data or output data for a command relatedthereto. The memory 1230 may include the volatile memory 1232 or thenon-volatile memory 1234.

The program 1240 may be stored in the memory 1230 as software, and mayinclude, for example, an operating system (OS) 1242, middleware 1244, oran application 1246.

The input device 1250 may receive a command or data to be used by othercomponent (e.g., the processor 1220) of the electronic device 1201, fromthe outside (e.g., a user) of the electronic device 1201. The inputdevice 1250 may include, for example, a microphone, a mouse, or akeyboard.

The sound output device 1255 may output sound signals to the outside ofthe electronic device 1201. The sound output device 1255 may include,for example, a speaker or a receiver. The speaker may be used forgeneral purposes, such as playing multimedia or recording, and thereceiver may be used for receiving an incoming call. According to oneembodiment, the receiver may be implemented as being separate from, or apart of, the speaker.

The display device 1260 may visually provide information to the outside(e.g., a user) of the electronic device 1201. The display device 1260may include, for example, a display, a hologram device, or a projectorand control circuitry to control a corresponding one of the display,hologram device, and projector. According to one embodiment, the displaydevice 1260 may include touch circuitry adapted to detect a touch, orsensor circuitry (e.g., a pressure sensor) adapted to measure theintensity of force incurred by the touch.

The audio module 1270 may convert a sound into an electrical signal andvice versa. According to one embodiment, the audio module 1270 mayobtain the sound via the input device 1250, or output the sound via thesound output device 1255 or a headphone of an external electronic device1202 directly (e.g., wiredly) or wirelessly coupled with the electronicdevice 1201.

The sensor module 1276 may detect an operational state (e.g., power ortemperature) of the electronic device 1201 or an environmental state(e.g., a state of a user) external to the electronic device 1201, andthen generate an electrical signal or data value corresponding to thedetected state. The sensor module 1276 may include, for example, agesture sensor, a gyro sensor, an atmospheric pressure sensor, amagnetic sensor, an acceleration sensor, a grip sensor, a proximitysensor, a color sensor, an infrared (IR) sensor, a biometric sensor, atemperature sensor, a humidity sensor, or an illuminance sensor.

The interface 1277 may support one or more specified protocols to beused for the electronic device 1201 to be coupled with the externalelectronic device 1202 directly (e.g., wiredly) or wirelessly. Accordingto one embodiment, the interface 1277 may include, for example, a highdefinition multimedia interface (HDMI), a universal serial bus (USB)interface, a secure digital (SD) card interface, or an audio interface.

A connecting terminal 1278 may include a connector via which theelectronic device 1201 may be physically connected with the externalelectronic device 1202. According to one embodiment, the connectingterminal 1278 may include, for example, an HDMI connector, a USBconnector, an SD card connector, or an audio connector (e.g., aheadphone connector).

The haptic module 1279 may convert an electrical signal into amechanical stimulus (e.g., a vibration or a movement) or an electricalstimulus which may be recognized by a user via tactile sensation orkinesthetic sensation. According to one embodiment, the haptic module1279 may include, for example, a motor, a piezoelectric element, or anelectrical stimulator.

The camera module 1280 may capture a still image or moving images.According to one embodiment, the camera module 1280 may include one ormore lenses, image sensors, image signal processors, or flashes.

The power management module 1288 may manage power supplied to theelectronic device 1201. The power management module 1288 may beimplemented as at least part of, for example, a power managementintegrated circuit (PMIC).

The battery 1289 may supply power to at least one component of theelectronic device 1201. According to one embodiment, the battery 1289may include, for example, a primary cell which is not rechargeable, asecondary cell which is rechargeable, or a fuel cell.

The communication module 1290 may support establishing a direct (e.g.,wired) communication channel or a wireless communication channel betweenthe electronic device 1201 and the external electronic device (e.g., theelectronic device 1202, the electronic device 1204, or the server 1208)and performing communication via the established communication channel.The communication module 1290 may include one or more communicationprocessors that are operable independently from the processor 1220(e.g., the application processor) and supports a direct (e.g., wired)communication or a wireless communication. According to one embodiment,the communication module 1290 may include a wireless communicationmodule 1292 (e.g., a cellular communication module, a short-rangewireless communication module, or a global navigation satellite system(GNSS) communication module) or a wired communication module 1294 (e.g.,a local area network (LAN) communication module or a power linecommunication (PLC) module). A corresponding one of these communicationmodules may communicate with the external electronic device via thefirst network 1298 (e.g., a short-range communication network, such asBluetooth™, wireless-fidelity (Wi-Fi) direct, or a standard of theInfrared Data Association (IrDA)) or the second network 1299 (e.g., along-range communication network, such as a cellular network, theInternet, or a computer network (e.g., LAN or wide area network (WAN)).These various types of communication modules may be implemented as asingle component (e.g., a single IC), or may be implemented as multiplecomponents (e.g., multiple ICs) that are separate from each other. Thewireless communication module 1292 may identify and authenticate theelectronic device 1201 in a communication network, such as the firstnetwork 1298 or the second network 1299, using subscriber information(e.g., international mobile subscriber identity (IMSI)) stored in thesubscriber identification module 1296.

The antenna module 1297 may transmit or receive a signal or power to orfrom the outside (e.g., the external electronic device) of theelectronic device 1201. According to one embodiment, the antenna module1297 may include one or more antennas, and, therefrom, at least oneantenna appropriate for a communication scheme used in the communicationnetwork, such as the first network 1298 or the second network 1299, maybe selected, for example, by the communication module 1290 (e.g., thewireless communication module 1292). The signal or the power may then betransmitted or received between the communication module 1290 and theexternal electronic device via the selected at least one antenna.

At least some of the above-described components may be mutually coupledand communicate signals (e.g., commands or data) therebetween via aninter-peripheral communication scheme (e.g., a bus, a general purposeinput and output (GPIO), a serial peripheral interface (SPI), or amobile industry processor interface (MIPI)).

According to one embodiment, commands or data may be transmitted orreceived between the electronic device 1201 and the external electronicdevice 1204 via the server 1208 coupled with the second network 1299.Each of the electronic devices 1202 and 1204 may be a device of a sametype as, or a different type, from the electronic device 1201. All orsome of operations to be executed at the electronic device 1201 may beexecuted at one or more of the external electronic devices 1202, 1204,or 1208. For example, if the electronic device 1201 should perform afunction or a service automatically, or in response to a request from auser or another device, the electronic device 1201, instead of, or inaddition to, executing the function or the service, may request the oneor more external electronic devices to perform at least part of thefunction or the service. The one or more external electronic devicesreceiving the request may perform the at least part of the function orthe service requested, or an additional function or an additionalservice related to the request, and transfer an outcome of theperforming to the electronic device 1201. The electronic device 1201 mayprovide the outcome, with or without further processing of the outcome,as at least part of a reply to the request. To that end, a cloudcomputing, distributed computing, or client-server computing technologymay be used, for example.

One embodiment may be implemented as software (e.g., the program 1240)including one or more instructions that are stored in a storage medium(e.g., internal memory 1236 or external memory 1238) that is readable bya machine (e.g., the electronic device 1201). For example, a processorof the electronic device 1201 may invoke at least one of the one or moreinstructions stored in the storage medium, and execute it, with orwithout using one or more other components under the control of theprocessor. Thus, a machine may be operated to perform at least onefunction according to the at least one instruction invoked. The one ormore instructions may include code generated by a complier or codeexecutable by an interpreter. A machine-readable storage medium may beprovided in the form of a non-transitory storage medium. The term“non-transitory” indicates that the storage medium is a tangible device,and does not include a signal (e.g., an electromagnetic wave), but thisterm does not differentiate between where data is semi-permanentlystored in the storage medium and where the data is temporarily stored inthe storage medium.

According to one embodiment, a method of the disclosure may be includedand provided in a computer program product. The computer program productmay be traded as a product between a seller and a buyer. The computerprogram product may be distributed in the form of a machine-readablestorage medium (e.g., a compact disc read only memory (CD-ROM)), or bedistributed (e.g., downloaded or uploaded) online via an applicationstore (e.g., Play Store™), or between two user devices (e.g., smartphones) directly. If distributed online, at least part of the computerprogram product may be temporarily generated or at least temporarilystored in the machine-readable storage medium, such as memory of themanufacturer's server, a server of the application store, or a relayserver.

According to one embodiment, each component (e.g., a module or aprogram) of the above-described components may include a single entityor multiple entities. One or more of the above-described components maybe omitted, or one or more other components may be added. Alternativelyor additionally, a plurality of components (e.g., modules or programs)may be integrated into a single component. In this case, the integratedcomponent may still perform one or more functions of each of theplurality of components in the same or similar manner as they areperformed by a corresponding one of the plurality of components beforethe integration. Operations performed by the module, the program, oranother component may be carried out sequentially, in parallel,repeatedly, or heuristically, or one or more of the operations may beexecuted in a different order or omitted, or one or more otheroperations may be added.

As described above, the embodiments of the disclosure:

1) Allow communication between PUEs by aligning their transmission andreception durations;

2) Provide mass pre-emption to avoid collisions with high prioritytraffic through mandatory slots;

3) Reduce the sensing burden on PUEs after pre-emption by allowing themto acquire replacement resources from the pre-empting UE;

4) Optimize the sensing duration for pre-emption and resourcereselection by partial sensing UEs to preserve their power:

5) Reduce the sensing burden on PUEs by reducing their monitoredduration for pre-emption based on traffic priority and CBR:

6) Dynamically enhance the alignment between Tx and Rx UEs forexchanging TBs through wake-up/sleep signaling;

7) Reduce the number of excluded resources due to the half-duplexconstraint thus allowing more resources for Step 2 of the Mode 2resource selection mechanism, thereby reducing chances of collisions andallowing the UE to meet its packet delay budget (PDB);

8) Provide better alignment between neighboring UEs through the exchangeof DRX information in mandatory slot (either from super UE to allneighboring UEs or between neighboring UEs);

9) Simplify the signaling of DRX ON cycles when overlapping with themandatory slots;

10) Dynamically allow/block the coexistence between PUEs and fullsensing UEs to render more resources accessible by PUEs while reducingthe potential for collisions between the resource reservations of PUEsand full sensing UEs;

11) Allow the usage of a more accurate CBR value for partial sensing UEsunlike LTE which uses a pre-configured value that is not related to theactual system occupancy level;

12) Reduce the probability of a PUE to be pre-empted by a full sensingUE through SCI indication of their limited power status;

13) Reduce collisions between partial sensing UEs and periodic/aperiodictraffic reservations of their neighbors by mandating minimum separationbetween consecutive transmissions to allow for pre-emption and resourcereselection triggering;

14) Allow UEs to obtain a more accurate estimate of the CBR value byoscillating between full and partial sensing; and

15) Allow UEs to have a better set of Y candidate slots for resourceselection by relying on CBR measurements thereby reducing the chances ofcollisions.

Although certain embodiments of the present disclosure have beendescribed in the detailed description of the present disclosure, thepresent disclosure may be modified in various forms without departingfrom the scope of the present disclosure. Thus, the scope of the presentdisclosure shall not be determined merely based on the describedembodiments, but rather determined based on the accompanying claims andequivalents thereto.

What is claimed is:
 1. A method performed by a partial sensing userequipment (UE), the method comprising: measuring resources within afirst window; determining a number of the measured resources having areceived signal strength indication (RSSI) greater than a firstthreshold; determining a channel busy ratio (CBR) based on the measurednumber of resources; and determining a channel occupancy ratio (CR)limit based on the determined CBR and transmission priority, whereindetermining the CBR based on the measured number of resources comprises:comparing a total number of measured resources within the first windowto a second threshold; and performing at least one of (a) or (b): (a) inresponse to the total number of measured resources within the firstwindow being less than the second threshold, determining the CBR as apre-configured CBR, and (b) in response to the total number of measuredresources within the first window being greater than or equal to thesecond threshold, determining the CBR based on a ratio of the number ofthe measured resources having the RSSI greater than the first thresholdto the total number of measured resources within the first window. 2.The method of claim 1, further comprising: measuring a CR of resourceswithin a second window; comparing the measured CR to the determined CRlimit; and performing a transmission, in response to the measured CRbeing less than the determined CR limit.
 3. The method of claim 1,wherein the pre-configured CBR is dynamically selected from among aplurality of CBR values preconfigured for a resource pool.
 4. The methodof claim 3, wherein the wherein the pre-configured CBR is dynamicallyselected from among the plurality of CBR values based on a priority ofthe partial sensing UE.
 5. The method of claim 3, wherein thepre-configured CBR is dynamically selected from among the plurality ofCBR values based on a last measured CBR.
 6. The method of claim 1,wherein the determined CBR is valid for a pre-configured duration.
 7. Apartial sensing user equipment (UE), the partial sensing UE comprising:a transceiver; and a processor configured to: measure resources within afirst window; determine a number of the measured resources having areceived signal strength indication (RSSI) greater than a firstthreshold; determine a channel busy ratio (CBR) based on the measurednumber of resources; and determine a channel occupancy ratio (CR) limitbased on the determined CBR and transmission priority, wherein theprocessor is further configured to determine the CBR based on themeasured number of resources by: comparing a total number of measuredresources within the first window to a second threshold; and performingat least one of (a) or (b): (a) in response to the total number ofmeasured resources within the first window being less than the secondthreshold, determining the CBR as a pre-configured CBR, and (b) inresponse to the total number of measured resources within the firstwindow being greater than or equal to the second threshold, determiningthe CBR based on a ratio of the number of the measured resources havingthe RSSI greater than the first threshold to the total number ofmeasured resources within the first window.
 8. The partial sensing UE ofclaim 7, wherein the processor is further configured to: measure a CR ofresources within a second window; compare the measured CR to thedetermined CR limit; and perform a transmission, via the transceiver, inresponse to the measured CR being less than the determined CR limit. 9.The partial sensing UE of claim 7, wherein the pre-configured CBR isdynamically selected from among a plurality of CBR values preconfiguredfor a resource pool.
 10. The partial sensing UE of claim 9, wherein thewherein the pre-configured CBR is dynamically selected from among theplurality of CBR values based on a priority of the partial sensing UE.11. The partial sensing UE of claim 9, wherein the pre-configured CBR isdynamically selected from among the plurality of CBR values based on alast measured CBR.
 12. The partial sensing UE of claim 7, wherein thedetermined CBR is valid for a pre-configured duration.
 13. A partialsensing user equipment (UE), the partial sensing UE comprising: aprocessor; and a non-transitory computer readable storage medium storinginstructions that, when executed, cause the processor to: measureresources within a first window; determine a number of the measuredresources having a received signal strength indication (RSSI) greaterthan a first threshold; determine a channel busy ratio (CBR) based onthe measured number of resources; and determine a channel occupancyratio (CR) limit based on the determined CBR and transmission priority,wherein the instructions, when executed, further cause the processor to:compare a total number of measured resources within the first window toa second threshold; and perform at least one of (a) or (b): (a) inresponse to the total number of measured resources within the firstwindow being less than the second threshold, determine the CBR as apre-configured CBR, and (b) in response to the total number of measuredresources within the first window being greater than or equal to thesecond threshold, determine the CBR based on a ratio of the number ofthe measured resources having the RSSI greater than the first thresholdto the total number of measured resources within the first window. 14.The partial sensing UE of claim 13, wherein the instructions, whenexecuted, further cause the processor to: measure a CR of resourceswithin a second window; compare the measured CR to the determined CRlimit; and perform a transmission, in response to the measured CR beingless than the determined CR limit.
 15. The partial sensing UE of claim13, wherein the pre-configured CBR is dynamically selected from among aplurality of CBR values preconfigured for a resource pool.
 16. Thepartial sensing UE of claim 15, wherein the wherein the pre-configuredCBR is dynamically selected from among the plurality of CBR values basedon a priority of the partial sensing UE.
 17. The partial sensing UE ofclaim 15, wherein the pre-configured CBR is dynamically selected fromamong the plurality of CBR values based on a last measured CBR.
 18. Thepartial sensing UE of claim 13, wherein the determined CBR is valid fora pre-configured duration.